{"paper_id":"2b9128a4-96ce-407c-8af7-159ba5b49eab","body_text":"Variations in deep-sea methane seepage linked to millennial-scale changes in bottom water temperatures ~50–6 ka, NW Svalbard margin | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Variations in deep-sea methane seepage linked to millennial-scale changes in bottom water temperatures ~50–6 ka, NW Svalbard margin Tine L. Rasmussen, Naima El bani Altuna, Erik Thomsen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4149143/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 27 Sep, 2024 Read the published version in Scientific Reports → Version 1 posted 12 You are reading this latest preprint version Abstract During the last glaciation, the northern hemisphere experienced profound millennial-scale changes (termed Dansgaard-Oeschger (DO) events) in atmospheric and oceanic temperatures. In the North Atlantic, the fluctuations resulted in extremely unstable bottom water conditions with bottom water temperatures (BWT) varying up to > 5°C. We have studied these environmental changes in a core from 1300 m water depth at Vestnesa Ridge, northwestern Svalbard margin to investigate a possible connection between BWT and seepage of methane from the seafloor covering the period ~ 50–6 ka. Beneath Vestnesa Ridge, gas hydrates containing vast amounts of methane are kept stable due to the high pressure and low temperatures. Release of gas is shown by numerous pockmarks on the seafloor. The pockmarks at 1300 m water depth are presently inactive, but they bear witness of earlier activity. Our study shows that from ~ 50–6 ka, the core site experienced repeated increases in BWT and in the emissions of gas, both following the pattern of the DO-events. This correspondence in time scale indicates that BWT was the primary forcing factor for the variability in methane release. However, the releases were delayed with up to > 1000 years compared to initial increase in BWT. Earth and environmental sciences/Biogeochemistry Earth and environmental sciences/Environmental sciences Earth and environmental sciences/Ocean sciences Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Numerous studies have shown that the northern North Atlantic including the Nordic Seas and Svalbard margin during the last glaciation, 50–12 ka, was affected by twelve abrupt temperature fluctuations 1 – 13 , which correlate closely with the millennial timescale Dansgaard-Oeschger (DO) events in the Greenland ice cores 14 , 15 . The DO events of cold stadials to warm interstadials reflect a series of abrupt warmings over Greenland of up to 16°C 16 . The main cause for the DO-events is repeated reversals of the Atlantic Meridional Ocean Circulation (AMOC) 1 , 4 , 7 , 8 , 12 , 17 (see below). The abrupt changes related to the DO events affected both the surface and the bottom water temperatures (BWT). During the glacial period BWT reached 5 to 5.5°C at 1200 to 1300 m water depth in in the Norwegian and Greenland Sea, respectively 8 , 12 , which is close to 6°C above present day temperatures. Methane, a powerful greenhouse gas, is presently released into the oceans from gas reservoirs located deep in the sediments on the continental margin. Most of the gas is trapped in ice in the Gas Hydrate Stability Zone (GHSZ) and kept stable by the high pressure and low temperature 18 . The GHSZ on the slopes can be several hundred meters thick and hosts vast amounts of gas hydrates 19 . High concentrations of gas hydrates generally occur deep in the sediments depending on the presence of sediments of high porosity 20 . Facilitated by faults and porous sediments, free and dissolved gas in the pore water can migrate upward through the GHSZ and through overlying sediments with the potential to reach the atmosphere 21 – 23 . Growing concern about the effect of greenhouse gases on the global warming, rising surface and deep ocean temperatures and on the increasing deep-ocean acidification 24 – 26 has fostered an intensified interest on the future stability of the GHSZ in a warmer ocean 23 , 27 – 31 . Several studies indicate that there is an overall correlation between variations in BWT and the intensity of the methane leaks 23 , 29 , 32 . Many other explanations have been suggested, viz., changes in hydrostatic pressure (sea level), tectonic activity/isostatic rebound, and sediment loading. However, concrete data from deep ocean sites are few 31 , 33 – 35 . In the present study we have reconstructed temperature fluctuations in a core from 1300 m water depth at Vestnesa Ridge on the northwestern margin of Svalbard margin covering the time-period ~ 50–6 ka. The purpose of the study was to investigate if there is a connection between BWT and the seepage of methane from the seafloor. The locality was selected because it represents a poorly known deep-water environment and more importantly, it includes the most unstable period of the last glaciation, 50–12 ka. This permits us to examine and compare gas hydrate stability during several warming and cooling events. Furthermore, the close connection between the oceanographic fluctuations in the North Atlantic and the temperature oscillations recorded in Greenland ice cores allows us to obtain a high degree of precision in the correlation of individual events. The study is based on 230 samples from marine core HH12-940PC (Fig. 1 a,b). The study comprises records of relative and absolute abundance of planktic and benthic foraminiferal species, concentration of ice rafted debris (IRD), planktic and benthic carbon and oxygen isotopes (δ 13 C and δ 18 O), and BWT calculated by transfer functions of the benthic foraminiferal census data. The general stratigraphy of the core was established based on fourteen AMS- 14 C dates and correlation to individual DO events in the Greenland NGRIP ice core. The reconstruction of changes in strength of methane seepage is based on carbon isotopes combined with foraminiferal and macrofaunal census data (chemosymbiotic bivalves). Carbonate nodules from authigenic precipitation of carbonates from methane seepage were also quantified and measured for carbon and oxygen isotopes. Millennial-scale temperature fluctuations in the Svalbard Margin. Bottom water temperature changes on the western Svalbard margin from ~ 50 to 12 ka are closely linked to the millennial time-scale climatic and oceanographic fluctuations that characterizes the North Atlantic region during the last glaciation 1 . These fluctuations are well documented in the Greenland ice cores as well as in North Atlantic sediment cores and a precise correlation between the two systems has been established 1 – 15 . This allows us to transfer the naming, numbering, and configuration of the DO events in the Greenland ice cores to the sediment cores of Vestnesa Ridge, including the warm interstadial events and the cold stadial events. In the marine records the stadials are defined by low benthic and planktic δ 18 O values, high content of ice rafted debris (IRD), and dominance of the polar planktic foraminiferal species Neogloboquadrina pachyderma 1 . The warm interstadials are defined by high benthic and planktic δ 18 O values, no or low IRD content, and low percentage of N. pachyderma 1 . Particularly cold and long lasting stadials in the marine records are termed Heinrich stadials (H). They mark prolonged IRD- events of icebergs released from the Laurentide Ice Sheet at 6–10 ka intervals referred to as ‘Bond’ cycles 1 . The causes for the millennial-scale fluctuations are generally attributed to instabilities in the strength and mode of the AMOC. Today, warm Atlantic Water of the Norwegian-Atlantic Current flows into the Nordic Seas at the surface (Fig. 1 a). It is cooled in winter and convects to form cold deep and intermediate water overflowing the Greenland-Scotland Ridge contributing to North Atlantic Deep Water 17 (Fig. 1 a). During the cold periods (stadials and Heinrich stadials) of the glacial period, the sea surface of the Nordic Seas and North Atlantic was covered by sea ice and icebergs and deep convection stopped 2 – 4 , 7 , 8 , 12 , 17 . However, below the cold sea surface, Atlantic water continued to flow into the North Atlantic and Nordic Seas here warming the intermediate and upper deep-water masses. The natural cold surface conditions were interrupted by abrupt warmings during which the oceanic circulation pattern reversed allowing warm Atlantic water to enter the North Atlantic and Nordic Seas at the surface (interstadials). In the Nordic Seas, deep convection was abruptly reestablished causing a renewed cooling of the intermediate and deeper water. Study area. Vestnesa Ridge is a southeast-northwest oriented ridge (05–08 °E) located at 79 °N at water depth between 1200 m to the east and > 1300 m to the west (Fig. 1 b). The ridge is in direct contact with cold intermediate water (-0.5°C) generated by the convection in the Nordic Seas 36 . The ridge is covered by thick contourite sediments, where core HH12-940PC was taken (Fig. 1 b). The crest of the ridge is marked by a series of pockmarks which at 1200 m water depth at the eastern part show intense seepage of methane 37 – 39 . The gas migrates upwards from a deep thermogenic reservoir through faulted chimneys below the pockmarks, and gas flares rise more than 800 m from the seafloor 38 , 40 . The western part is apparently less active as indicated by the presence of several inactive pockmarks with no visible flares 39 . The base of the GHSZ is located ~ 160–180 m below the sediment surface 39 . The GHSZ is several hundred meters thick 41 and gas hydrates have been found up to a few meters below the sediment surface in some of the active pockmarks in the eastern part 40 , 42 , 43 . The sulfate-methane transition zone (SMTZ) designating the transition of anaerobic oxidation of methane by archaea and sulfate-reducing bacteria 44 is located > 2–~10 m below present sediment surface on the western inactive part indicating little or no seepage 42 . Core HH12-940PC was taken from a sediment-filled pockmark at 1294 m water depth from the western part of Vestnesa Ridge (79.08 °N, 05.36 °E) (Fig. 1 ) (from here on termed core 940). This part of the ridge was active in the past, but is presently inactive 37 , 39 , 45 . To test our results, we compare the records from core 940, with records from nearby core HH15-1252PC taken north of Vestnesa Ridge (from here on termed core 1252), which has been unaffected by seepage of methane 12 (Fig. 1 b). Core 1252 covers the same period as core 940. It furthermore comprises a quantification of BWT based on the Mg/Ca ratio of benthic forminifera. The sediments at both core sites consist mainly of fine-grained hemipelagic mud and clayey silts. Results Twelve out of 14 AMS- 14 C dates are in chronological order (Fig. 2 ; Table 1; Figs. S1–S2). With eight species of planktic and more than 100 species of benthic foraminifera (Table S1 ), the overall diversity of the benthic foraminiferal faunas is quite high (Figs. 3 – 5 ). During most stadial intervals several benthic species of boreal to subtropical affinity termed the Atlantic Species Group, appears 9 , 12 , 46 (see Methods; Fig. 5 ; Figs. S3, S4). Stratigraphy and identification of Dansgaard-Oeschger events. The AMS- 14 C dates in combination with the δ 18 O record indicate that the core comprises the mid-late part of marine isotope stage (MIS) 3, the whole of MIS 2 and the early part of MIS 1 (mid-late Weichselian to mid Holocene) (Fig. 3 a,b). Based on the lowermost two dates and assuming linear sedimentation rate, the oldest sediments of the core are calculated to ~ 50 ka (Fig. 2 ). Similarly, from the uppermost two dates, the youngest sediments are calculated to ~ 6.3 ka. The lower part of the core from 838 to 630 cm is referred to MIS 3 (Figs. 3 , 4 ). This interval shows high variability of most parameters including stable isotopes (δ 18 O and δ 13 C; Fig. 4 ), BWT, the percentages of the dominating planktic and benthic species N. pachyderma , Cassidulina neoteretis , Melonis barleeanus , and Cassidulina reniforme and BWT (Figs. 3 e, 4 a,b, 5 ; see also Supplementary text). A similar pattern is seen in core 1252 north of Vestnesa Ridge (Fig. 5 ; Fig. S4). Stadials are identified by low planktic and benthic δ 18 O, high content of IRD, and dominance of the polar planktic species N. pachyderma . Interstadials are identified by high δ 18 O, no/low IRD and lower percentages of N. pachyderma . The BWT in MIS 3 shifts between low temperatures during the interstadials and high temperatures during the stadials (Figs. 4 b, 5 a,f). The composition of the benthic foraminiferal faunas shows that the interstadials are dominated by M. barleeanus , Nonionella spp., Stainforthia spp., and C. reniforme , whereas the stadials are dominated by C. neoteretis and/or the Atlantic Species Group (Fig. 5 ; Fig. S4). The changes in relative abundance of the planktic species N. pachyderma is typical for the Nordic Seas where it reflects shifts in influence of cold polar surface water, and warm Atlantic water 1 – 4 , 6 (Fig. 4 a). The variability encountered in core 940 is characteristic for mid-late MIS 3 and MIS 2 in the Nordic Seas and North Atlantic and it allows us to identify Heinrich stadials H5, H4 and H3 as well as DO events 12–5 of MIS 3 1–9,12,14–16 . Our identification to specific DO events is confirmed by correlation of core 940 to the δ 18 O record of the NGRIP ice core where these events are defined and dated. Furthermore, the stratigraphy of core 940 is quite similar to that of nearby core 1252 12 (Figs. 2 b, 5 ; Figs. S3, S4) (see Methods). The early part of MIS 2 is very compressed with low sedimentation rates (Fig. 2 c). We can, nevertheless, recognize interstadials 4, 3 and 2, plus H2, the last glacial maximum (LGM) and H1 (Figs. 2 – 5 ). The LGM comprises the core section from 585.5–570.5 cm, where it is recognized by the very high planktic and benthic δ 18 O values. The LGM is dated to ~ 24.0–17.5 ka (Fig. 2 a,b) correlating well with the global isotope stack record 47 . The LGM is followed by H1 from 570.5–560.5 cm marking the beginning of the deglaciation dated to ~ 17.5–14.7 ka 43 (Fig. 2 a,b). It is characterized by minima in the benthic and planktic δ 18 O values and a high relative abundance of the Atlantic Species Group (> 12%) (Figs. 3 a,b, 5 e,j). The low δ 18 O values and the occurrence of the Atlantic Species Group is typical for H1 in the North Atlantic, Nordic Seas and Arctic Ocean 4 , 8 , 9 , 12 , 46 . The warm interstadials Bølling and Allerød 560.5–270.5 cm and dated to 14.7–~13.0 ka (Figs. 2 a,b, 3 ), show an expanded section and very high sedimentation rates with an average of 160 cm/ka as compared to 2 cm/ka for the LGM and H1 (Fig. 2 c). The Bølling and Allerød section appears quite disturbed with vertical channels/fractures (Fig. S1 ; see discussion). The Younger Dryas cold stadial from 270.5–225.5 cm and dated to ~ 13.0–11.7 ka is distinguished by low planktic and benthic δ 18 O values (Figs. 2 , 3 a,b). The Holocene interval from 225 cm to core top and dated to 11.7–6.3 ka (Fig. 2 ) is first of all distinguished by low percentages of the polar planktic species N. pachyderma and low planktic and benthic δ 18 O values (Fig. 3 a,b,e) and high concentrations of planktic and benthic foraminifera (Fig. S2d,e). The benthic foraminifera C. wuellerstorfi is relative abundant in the Holocene part (Fig. 3 f). Furthermore, core 940 shows several distinct lithological features that clearly have stratigraphical value as they occur in numerous other records from the western Svalbard margin and always at the same stratigraphical position 9 , 10 , 12 , 40 . These features comprise a debris flow/IRD deposit from the last glacial maximum dating ~ 24.0 ka (582.5–575.5 cm down core), a laminated horizon deposited during the Bølling interstadial dating ~ 14.5 ka (430–480 cm down core), and an early Holocene diatom layer dating ~ 10.0 ka (175–180 cm down core) (Fig. 3 ; Fig. S2). δ 13 C and temperature variability in cores 940 and 1252. The δ 13 C values of marine organisms are strongly affected by methane in the environment. Tests of the majority of intermediate infaunal ( M. barleeanus ) to shallow infaunal ( C. neoteretis ) benthic foraminiferal species living in non-seep environments show interglacial values of δ 13 C between − 1 and 0‰ 48 and glacial values between − 2 and 0‰ 12 . The epifaunal species C. wuellerstorfi records glacial and interglacial values of 0 to > + 1‰ 48 (Fig. 3 d). Values lower than about − 2‰ are usually taken to indicate the presence of methane assuming that these foraminifera would obtain the low δ 13 C values either from the surrounding pore water or from consumed food 49 – 51 . In the following descriptions, the − 2–0‰ interval is termed the typical glacial-interglacial range for the infaunal species C. neoteretis and M. barleeanus combined and used as a visual guideline in the presentation (grey vertical bar in Fig. 4 e). Comparison of the results of core 940 with previously published data from core 1252 covering the interval ~ 50 to 12 ka, we find the same distribution of benthic and planktic δ 18 O, the same bottom water temperatures, and the same relative abundances of benthic foraminiferal species 12 . This allows a close correlation of the two records comprising H1–H5 and DO events 12–2 (Fig. 5 , Figs. S3, S4). However. with respect to δ 13 C the two sites are very different. In contrast to the fluctuating values of core 940 (Fig. 4 e), all δ 13 C values of core 1252 are within the typical range of -2–0‰ confirming that site 1252 was without any traces of methane seepage 12 (Fig. 5 k). The lack of methane is further supported by the absence of carbonate nodules and chemosymbiotic mollusks, both common in core 940 (see discussion). One of the most conspicuous features of core 940 is the that the δ 13 C forms a pattern that mimic the pattern shown by the δ 18 O of the DO events in the Greenland ice cores with low values in the first interstadial above the Heinrich stadials and increasing values towards the next Heinrich stadial. The pattern corresponds to Bond-cycles 1 (see introduction) (Fig. 4 ). The lowest benthic values occur close to the stadial/interstadial boundaries - mostly at the beginning of the interstadials but sometimes at the end of the stadials (e.g., top of H5, S12 and H1; Fig. 4 e). From this low point the δ 13 C values increase during the interstadial, but they generally remain below the typical range of -2–0‰. At the stadial boundary the values increase further and the values of the stadials are usually higher than the interstadial values and mostly above − 3‰ (Fig. 4 e). The Younger Dryas stadial show values above − 2‰ (Fig. 3 d). The planktic δ 13 C record of core 940 shows low values at the beginning of many interstadials, but not as consistently as in the benthic records. Moreover, it appears that several of the planktic minima occur slightly later than the benthic minima and are of much lower magnitude (Fig. 3 a–d). In core 940 many of the interstadials (though not all) display a high concentration of carbonate nodules (Fig. 4 c; Fig. S2c). These nodules are characterized by very low δ 13 C values (-47.2 to -30.6‰; average − 41‰) and high δ 18 O values (5.7 to 7.2‰; average 6.7‰). Core 940 also contains layers rich in chemosymbiotic bivalves and other seep-associated macrofaunas. In addition to higher δ 13 C (>-3‰), these faunas co-occur with low benthic δ 18 O and higher BWT (Figs. 3 , 4 b–d, Fig. S2). They are found in relatively thin discrete layers in stadials S12 and S6 and in H5, H4, H3, H2 and H1 (Fig. 3 ). The chemosymbiotic faunas are absent from the interstadials just as they are absent from the non-seep core 1252 12 . In core 940, the increase in bottom water temperature from interstadials to stadials varies from 1.2°C between interstadial IS6 and stadial S6 to 4.7°C between LGM and H1 (Fig. 6 a). In core 1252, the increases vary from 1.0°C between IS7 and S7 to 5.7°C between LGM to H1 (Fig. 6 b). For both cores, the temperature rises are largest in connection with the Heinrich stadials. The temperatures generally decrease successively in the subsequent stadials until the next Heinrich stadial, reflecting the pattern of the Bond cycles 1 (Fig. 6 ). The calculated temperatures represent the maximum difference from the lowest temperature during the interstadials to the highest temperature during the subsequent stadial. The average rate of the temperature increases is 2.0°C/ka (range 1.1–3.2°C/ka) for core 940 and 1.9°C/ka (range 1.4–2.5°C/ka) for core 1252 (Fig. 6 a,b). Discussion Dansgaard-Oeschger events and the emission of methane. The consistent millennial time-scale pattern shown by the δ 13 C events in core 940 strongly indicate that the events are not randomly distributed and that they are caused by a common forcing factor which varies concurrent with the DO oscillations. The most likely factor on the Vestnesa Ridge that fulfils these criteria is bottom water temperature which in the North Atlantic and Nordic Seas also fluctuates according to the DO events 4 , 7 – 9 , 12 , 46 . However, other factors such as tectonism/isostatic rebound, and hydrostatic pressure are also briefly discussed. Glacial and interglacial δ 13 C values below the typical ranges of benthic foraminiferal species have generally been used to indicate the presence of methane 49 , 51 . The immediate interpretation of the variation of δ 13 C in core 940 is that the seepage of methane was low to moderate during the stadials where the δ 13 C values generally are above ~-3‰ (Fig. 4 e). An abrupt decrease in δ 13 C close to the stadial/interstadial transitions suggests that the seepage of methane at the beginning of the interstadials increased significantly. The peak was short-lasting, but the emission remained relatively high during the rest of the interstadials (Fig. 4 e). Note that after ~ 10 ka in the Holocene high δ 13 C values in core 940 indicate a reduction or stop in seepage (Fig. 3 c,d). Overall, it is important to note that the δ 13 C values in core 940 are consistently lower than in core 1252 revealing that site 940 constantly was affected by methane also during the stadials (Figs. 4 e, 5 k). The δ 13 C values of live benthic foraminiferal tests that have been exposed to methane generally range from 0 to -6 to -8‰, depending on species, indicating that the effect of methane on the δ 13 C in shells of foraminifera is relatively small 34 , 49 , 50 , 52 , 53 , This is especially evident when compared to the much lower values (-10‰ to <-20‰) measured in foraminiferal tests affected by authigenic carbonate 40 , 54 , 55 . These coatings, which usually are precipitated on dead tests, are particularly common in methane affected environments, where the precipitation is a result of anaerobic oxidation of methane and sulfate in the SMTZ 44 , 52 , 56 . The process releases bicarbonate and hydrogen sulfide. The δ 13 C measurements in this study are based on well-preserved pristine-looking tests. It is nevertheless conceivable that some tests could have had invisible coatings on their inside affecting the original δ 13 C values of the living foraminifera. Given the low δ 13 C we obtained in the calcareous nodules (Fig. 4 c–e), it is possible that even a thin coating could affect some of the measured foraminiferal values. The δ 18 O values are elevated in the nodules compared to the benthic foraminiferal values but we note that our measured δ 18 O values are similar to and not higher than the values from the non-seep core 1252 (Fig. 4 d, Fig. S3a,d) and other Nordic Seas non-seep records 3 , 4 , 8 , 9 , 12 . We point out that if the δ 13 C values of the foraminifera were dominated by values from authigenic carbonates precipitated at a migrating SMTZ level, we would expect a random distribution of the δ 13 C values and not the clear correlation to the DO climatic events we see (Fig. 4 e). The validity of the δ 13 C curve of core 940 as reflecting changes in the emission of methane is supported by several other studies from the Nordic Seas. In core PS62/015 − 3 from a methane seep at 980 m water depth in Denmark Strait, Millo et al. 34 observed a similar stratigraphic distribution of low δ 13 C values (Fig. 1 a). In a section referred to MIS 3, the researchers found low δ 13 C in the major interstadials of IS17 to IS8 in a pattern similar to ours and in the long-lasting Heinrich stadials and stadials of MIS 5 and MIS 3, the methane was released before the end of the events similar to H5, S12 and H1 in core 940, while in shorter lasting events the increase was limited to the subsequent interstadial phases 34 (Fig. 4 ). Moreover, a comparable distribution of δ 13 C values occurs in Heinrich stadials H4, H3 and H2 in core HH12-930GC from the active pockmark field at 1200 m water depth on the eastern part of Vestnesa Ridge 57 (Fig. 1 b). It is also important to notice that core 940 is characterized by many carbonate nodules which occur exclusively in the interstadials indicating that methane oxidizing and sulfate reducing microbes were active 44 (Figs. 3 , 4 ). The very low δ 13 C values signal a strong discharge of methane 58 and the increased δ 18 O values of the nodules indicate gas hydrate dissociation 59 – 61 (Fig. 4 d,e). New research indicates that such nodules in periods with strong seepage tend to form near or at the sediment surface, although they at low seepage also can form deeper in the sediment but at a low rate 56 , 59 , 62 – 63 . A case study of multicore MUC12 from the eastern active pockmarks at Vestnesa Ridge in a location of strong seepage and presence of bacterial mats, the SMTZ was located 0–1 cm below the seabed 50 (Fig. 1 b). Total alkalinity was at maximum at 0 cm. The rates of sulfate reduction were at maximum at 0–3 cm below the seabed and methane oxidation rate was at maximum at 3 cm depth. Additional evidence on changes in the environmental conditions during the investigated period are found in the chemosymbiotic bivalves. They rely on hydrogen sulfide for metabolism. They occur mainly in areas of low to moderate seepage and are absent in areas with intense seepage and toxic levels of sulfide 63 – 65 . In core 940, they are recorded only in layers correlating with the major stadials and Heinrich stadials of δ 13 C above − 3‰ and being absent in the interstadials (Fig. 4 c). This is in good agreement with the interpretations presented above of modest seepage during stadials and Heinrich stadials and strong seepage during interstadials. Timing, and magnitude of increased seepage. In this investigation we have shown that during the period 50–12 ka, the highest emissions of methane occurred when the bottom water was coldest (< 0–2°C), while the lowest occurred when the bottom water was warmest (3–>5°C). This is opposite to nearly all modern observations from shallow sites which find that there is an immediate positive correlation between water temperature and the dissociation of gas from gas hydrates 23 , 30 , 32 , 66 – 69 . However, it agrees with model experiments from deep sites which indicate that up to several thousands of years can pass from warming to increased gas release 68 , 69 . The stadials in the Nordic Seas are distinguished by increasing bottom water temperatures, surface water stratification and dense cover of sea ice 11 – 13 . However, the seepage of gas remained low to moderate until the very end of the stadials signifying that the higher temperatures first at that point in time reached the deep, high concentrations of gas hydrates. In terms of years, the delayed reaction relative to the first rise in water temperatures is in the order of 500 to > 1000 years. The warm bottom water is at the beginning of the interstadials rapidly replaced by cold bottom water 4 , 7 – 9 , 12 (Fig. 5 a,f). The response in gas emission to the cooling is delayed with a time factor that resembles the delayed response to the warmings at the beginning of the stadials (Fig. 4 b,e). The deposits of the Bølling-Allerød interstadials are disturbed from 520–260 cm with obliterated sediment structures, abundant pyrite, and a dominance of poorly preserved and apparently reworked foraminifera (Fig. S2c, see Methods). The reworked faunas include many large, abraded specimens of C. wuellerstorfi (Fig. 4 f). The most likely cause for these disturbances is turbulence instigated by an intense emission of methane. Upward gas migration is also indicated by the vertical channels in the sediment and by the chaotic isotope values and a fauna distribution pattern with many horizons totally without foraminifera (Fig. 3 , Figs. S1, S2). A possible analogue situation could be a human-induced blowout crater from a gas pipe outburst in the North Sea, where small, dead foraminiferal shells were brought in suspension and removed from the area resulting in a local enrichment of large forms 53 . An extraordinary strong seepage during the Bølling-Allerød interstadials is not surprising considering that the preceding Heinrich stadial H1 experienced the highest bottom water temperatures recorded in the history of core 940 (Figs. 4 b, 6 a,b). Widespread occurrences of low δ 13 C values during the Bølling-Allerød interstadials indicate that similar emissions occurred simultaneously over large areas of the western Svalbard margin 40 , 55 including shelf areas 29 . Another contributory cause to the widespread and strong emission of methane during the Bølling and Allerød interstadials could be tectonic movements due to the proximity of the Knipovich Ridge spreading zone 37 , 45 , 70 , isostatic rebound 71 – 73 and/or high sedimentation rates 35 . However, the fact that the changes in gas seepage occurs on a millennial time scale, suggests that the primary trigger most likely was the high BWT. Tectonism/isostatic rebound have slower response times and may have prolonged the periods of seepage. During MIS 3 the surrounding ice sheets were small and mainly located inland 74 , 75 and the millennial-scale events were probably too short to induce substantial effects from tectonism/isostatic rebounds. Furthermore, sea level changes were small during DO events 76 and the effect of changes in hydrostatic pressure is small at this water depth 77 . Compared to modern observations of a positive relationship between bottom water temperatures and the dissociation of methane from gas hydrates, the nearly inverse relationship disclosed in core 940 is surprising. Nevertheless, the inverse correlation is repeated 12 times, one for each DO event, and we consider the finding to be reliable, also because a similar pattern was found at other seep sites 34 . The results of core 940 indicate that the inverse relationship is caused by a time lag that most likely is caused by a delay in the transport of heat through the sea bottom sediments. There are no published diffusion rates from Vestnesa Ridge, but a heat-flow model by Karstens et al. 35 for the last deglaciation from the deep-sea Nyegga pockmark area indicated a delay of 1000 years before heat induced by increased sedimentation rates (> 10 m/ka) reached the gas hydrates and an almost explosive seepage of methane occurred (Fig. 1 a). In core 940, the time lag between the first warming of the bottom water and the response in methane emission generally varies between 500 and 1000 years although the data suggest that delays of close to 2000 years may have occurred. Our interpretation of the cause for the inverse relationship at site 940 is in good agreement with several studies of present-day methane emission released by warming bottom water. The results of these studies indicate that the slow diffusion of heat and gas through the sediment column can delay the emission of methane with hundreds to thousands of years relative to the initial warming 28 , 33 , 35 , 68 , 69 . The temporal estimates in these studies are based on modeling experiments as field data of modern diffusion rates are highly uncertain or completely missing 28 , 69 . Implications . We have studied variations in methane emission at a site from 1294 m water depth northwest of Svalbard for the period ~ 50.0–6.3 ka. The most significant environmental events are repeated changes in bottom water temperatures and strong release of methane for approximately every 500–2000 years. The temperature rises and emission of methane is in almost exact antiphase. We interpret the delay between temperature and methane emission as caused primarily by a slow diffusion of heat through the sediments. The increase in BWT during the twelve DO events at Vestnesa Ridge ranges from 1.2–4.7°C (Fig. 6 ). The average temperature increases from the cold interstadials to the maximum temperature obtained in the stadial/Heinrich stadial is 2°C/ka (Fig. 6 a). The ocean today has taken up 90% of the atmospheric heating from present global warming (see references in ref. 25) and the deep ocean is rapidly warming 25 , 78 , 79 . Deep water at 700–2000 m water depth is predicted to warm by 0.2°C over the next 50 years 79 which corresponds to 4°C/ka. This is twice the calculated average rate for the interstadial/stadial (Heinrich stadial) transitions in cores 940 and 1252 (Fig. 6 ). At Vestnesa Ridge, bottom water warmings with temperature rises of ~ 3–5°C continued for 500 to > 1000 years before the emission of methane started to increase and reached a level sufficient for the rapid formation of authigenic carbonate. Transferred to modern conditions at the site, this would suggest that the present warming of the deep oceans could reach similar temperatures and remain warm for several hundreds of years before we would see any significant reaction in the dissociation of the gas from the buried gas hydrates. However, it also implies that the emission would continue for many years after a stop in the discharge of anthropogenic CO 2 and a subsequent temperature fall. Methods Core handling and logging . Piston core HH12-940PC was taken from a sediment-filled pockmark at 1294 m water depth from the western field of inactive pockmarks on Vestnesa Ridge, northwestern Svalbard margin during a cruise with RV Helmer Hanssen in July 2012. The upper part of the 12 m inner core liner imploded at the top and the upper ~ 1 m of sediment was severely disturbed and discarded. The lower 838 cm were intact and appeared undisturbed. The sediments consisted mainly of fine-grained hemipelagic mud and glacimarine coarse, or clayey deposits. However, the interval 545 to 260 cm showed several vertical channels or fractures, and the interval 520 to 260 cm had foraminifera barren intervals and reworked, abraded benthic specimens were occasionally observed (Fig. S1 ). Core HH12-940PC was logged using a GEOTEK Multisensor Core Logger with a mounted loop sensor for magnetic susceptibility before opening at the Department of Geosciences, UiT the Arctic University of Norway, Tromsø, Norway (Fig. S2a). The core sections were X-rayed on a GEOTEK Standard X-ray CT System (Fig. S1 ). After opening the sections were color imaged with a Jai L-107CC 3 CCD RGB line scan camera installed on an Avaatech XRF core scanner (Fig. S1 ). The lithological log was obtained based on the GEOTEK logs and X-ray images in combination with sediment visual description and color (Munsell chart) shortly after splitting the sections, the grain size distribution and counts of ice rafted debris (IRD) (see below). Sampling and counts of foraminifera and IRD. The entire core was initially sliced in 1-cm samples, weighed, freeze-dried, and weighed again. Samples at 5 cm intervals were taken out and subsequently wet sieved over mesh-sizes 0.063, 0.1, and 0.5 mm. A second round to double the sample resolution to 2.5 cm sample intervals was later done in the lower part > 545 cm. In the interval 570–555 cm samples at every cm were taken out. All new samples were treated in the same way as the first sample batch. All unsplit sample residues > 0.1 mm was spread evenly on a picking tray. Foraminifera were picked from randomly chosen squares until > 300 specimens of benthic and > 300 specimens of planktic foraminifera were obtained. The foraminifera were identified to species level (some samples contained too few specimens for quantification). The percentages of benthic and planktic species were calculated separately. The size fraction > 0.1 mm was chosen to obtain both small phytodetritus species like Epistominella and Nonionella species and larger important paleoenvironmental indicator species like e.g., Melonis barleeanus , and Cibicidoides wuellerstorfi (see species list in Table S1 ). A total of eight planktic species and > 100 benthic species were identified. Benthic foraminiferal species of subpolar to subtropical affinity e.g., Sigmoilopsis schlumbergeri , Discospirina italica , Opththalmidium inconstans , Eggerella bradyi , Tosaia hanzawaia , Cibicidoides pachyderma , Epistominella decorata , Gyroidinoides neosoldanii , and Gyroidina umbonata belonging to an association of subtropical to boreal species and defined as the Atlantic Species Group were added together 4 , 8 , 12 , 46 (Table S1 ). The concentration of planktic and benthic specimens was calculated as number/g dry weight (dwt) sediment (Fig. S2d,e). Ice rafted debris (IRD) were counted in the > 0.5 mm size fraction. Number of IRD grains per g dwt sediments was calculated (Fig. S2b). Carbonate-encrustations (nodules) from authigenic precipitation of carbonates from methane seepage and pyrite particles were also counted in the > 0.5 mm size fraction and concentrations calculated (Fig. 4 c, Fig. S2c). Transfer functions on the benthic foraminiferal fauna. In core 940 bottom water temperatures (°C) were estimated by transfer functions using the C2 program 80 . The calculations were based on the > 0.1 mm size fraction of benthic foraminifera. We applied the MAT (Modern Analogue Technique) method using 30 analogues. For the calculations we used a database of 401 samples modified from ref. 9 (see references therein). The material consists of previously published records on the distribution of benthic foraminifera in the Nordic Seas and in the northern North Atlantic Ocean. For the calculations we used only samples from the depth interval 250–~2000 m. Macrofaunal counts . Presence and quantification of macrofaunas, large foraminifera and pteropods were examined from the > 0.5 mm size fractions. Chemosymbiotic bivalve species of Archivesica arctica , Isorropodon nyeggaensis , Rhagothyas kolgae and Acharax svalbardensis (see Fig. 4 , Fig. S2) were found in distinct thin layers, while others such as rissoid gastropods, other gastropods, Yoldiella spp. and Thyasira spp. were found more scattered in the record. Large bivalves were often broken but hinges were mostly intact and counted as representative of a shell, because eventual paired (but later separated) shells were not easy to match based on hinges alone. Paired shells of Yoldiella spp. and Thyasira spp. were common but counted as two to match with other un-paired shell counts. Stable isotopes. In core HH12-940PC, stable isotopes δ 13 C and δ 18 O were measured in the polar planktic foraminiferal species Neogloboquadrina pachyderma , and benthic species Cibibidoides wuellerstorfi , Melonis barleeanus , and Cassidulina neoteretis . Only pristine-looking specimens with no visible coating (authigenic precipitation of carbonate, see text for explanation) were picked under a binocular microscope. Several samples in the mid-section 555–270 cm contained few benthic and planktic specimens and several foraminiferal specimens were poorly preserved, abraded, fragmented, or coated with authigenic material, therefore in this part benthic isotope analyses were few. Also, deeper in the core some samples were devoid of pristine benthic specimens leaving gaps in the records (marked by black vertical bars in Fig. 4 e). The specimens from the first sample set collected at 5 cm intervals were analyzed using a Kiel IV-MAT 253 at the Department of Earth Science, University of Bergen, Bergen, Norway. Long-term external precision (1σ error), based on the replication of working standards pooled over a period of weeks to months, is ≤ 0.04‰ and ≤ 0.08‰ for δ 13 C and δ 18 O, respectively. Results are reported on the VPDB (Vienna Pee Dee Belemnite) scale and referenced to this scale using NBS-19, NBS-18, and internal house standard CM12 (Table S2). The samples from the second sample set were analyzed using a thermoScientific Gasbench II, MAT 253 IRMS at the Department of Geosciences, UiT the Arctic University of Norway, Tromsø, Norway. The precision of the instrument with 1σ error is < 0.1 for both δ 13 C and δ 18 O on calcite. Three standards were used: Isolab A, Isolab B, and Merck CaCO 3 (Table S2), each reported on the VPDB scale relative to NBS-18, NBS-19 and LSVEC (Table S2). Because of isotopic disequilibrium, the δ 18 O values of C. wuellerstorfi was corrected by + 0.64‰ and M. barleeanus by + 0.4‰ 81,82 . The δ 18 O values of the benthic species C. neoteretis and the planktic species N. pachyderma were not corrected. Calculations of bottom water temperature increases and rate of increases . For both cores the calculation of temperature increases were based on the δ 18 O values by taking the difference between the maximum δ 18 O values at the end of an interstadial and the minimum values obtained in the subsequent stadial/Heinrich stadial. The calculated differences were corrected for the ice volume change using the sea level curve of ref. 76. For core HH15-1252PC we also calculated the temperature differences between the interstadials and stadial/Heinrich stadials using the minimum Mg/Ca temperature and maximum Mg/Ca temperature for each DO event. We refrained from using the temperatures calculated by transfer functions in core HH12-940PC. In the Svalbard region, the calculations based on benthic species seem to slightly overestimate the lowest temperatures between − 1 and 1°C 9 . The rates of temperature increases were calculated for each event by dividing the calculated ranges of temperature rises by the time of minimum temperature to the maximum based on the NGRIP ice core age model 14 . AMS- 14 C dates. In core HH12-940PC, samples of monospecific N. pachyderma , chemosymbiotic bivalves, and small non-chemosymbiotic bivalves were dated (Table 1). In two cases, the levels dated by N. pachyderma were also dated using chemosymbiotic bivalves. Mixed planktic and benthic foraminiferal faunas were dated in intervals where dateable material was scarce, sometimes supplemented by small specimens of non-chemosymbiotic bivalves (Fig. 3 e; Table 1). We allow these datings based on mixed benthic and planktic material, because there is only a small difference in reservoir effect between surface and bottom in the Nordic Seas 4 , 8 , 9 , 12 , 17 . The AMS 14 C dates were performed at the 14Chrono Centre, Queen’s University, Belfast, Northern Ireland, UK. To calibrate the radiocarbon ages, we used the approach presented in Heaton et al. 83 which accounts for some latitudinal and regional uncertainties related to 14 C depletion during glacial periods. We extracted the average regional marine radiocarbon reservoir age (ΔR) from the http://calib.org/marine/ database based on the seven nearest modern-day ΔR. This resulted in a ΔR=-65 ± 33 14 C years for our study area (Table 1). Individual samples were then calibrated using the IntCal 0.3.1 package ( https://cran.rproject.org/web/packages/IntCal/IntCal.pdf ). We used Bayesian age-depth modelling (Table 1), the Marine20 calibration curve 83 and the rBacon 3.1.1 package 84 in R software for the age-depth plot (Fig. 2 a). The ages in this paper is presented using the modern ΔR. The mid-points of obtained age ranges were chosen, and calibrated ages are reported with 1σ error (Fig. 2 a; Table 1). To test our identification of individual DO events and their subdivision into stadials/Heinrich stadials and interstadials, we correlated the events in core 940 to the same events as they are defined in the δ 18 O record of the NGRIP ice core (Fig. 2 b) and to the events in nearby marine core 1252 12 (Fig. 5 , Figs. S3, S4). While the identification of the individual DO events in the two marine cores appear straightforward, it is evident that there is a divergence between the calibrated ages of the events in the marine cores and their ages in the NGRIP time scale. This time difference amounts of ~ 1000 years in MIS 2 and parts of MIS 3 undoubtedly reflecting an increase in the reservoir age during the glacial (Fig. 2 b). We refrain from plotting our data on an age scale as the profound changes in sedimentation rates stretches some intervals while compressing others making figures difficult to overview (Fig. 2 b,c). Declarations Competing interests: The authors declare no competing interests. Author Contribution The study was developed by TLR and ET. TLR, NEA, and ET provided the data. The original draft was written by TLR, and all authors participated in writing and editing Acknowledgement We thank the captain and crew of RV Helmer Hansen and participants of cruise GEO-8144/3144 in 2012 for their assistance in core retrieval and handling. The cruise was funded by the Research School in Arctic Marine Geology and Geophysics (AMGG, the Arctic University of Norway, Tromsø). The study was funded by the Research Council of Norway through its Centers of Excellence funding scheme, grant number 223259. Ulysses Ninnemann supervised the stable isotope measurements in Bergen and Matteus Lindgren the measurements in Tromsø Data Availability The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request. 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Wallmann, K. et al . Gas hydrate dissociation off Svalbard indicated by isostatic rebound rather than global warming. Nat. Comm. 9. doi: 10.1038/s41467-017-02550-9 (2018). Daszinnies, M. et al . Plio-Pleistocene seepage history off western Svalbard inferred from 3D petroleum systems modelling. Mar. Petrol. Geol. 128. doi: 10.1016/j.marpetgeo.2021.105023 (2021). Vachon, R. et al . Glacially induced stress across the Arctic from the Eemian interglacial to the present – implications for faulting and methane seepage. JGR Solid Earth 127. doi: 10.1029/2019JG005371 (2022). Lambeck, K., Purcell, A., Zhao, J. & Svensson, N. -O. The Scandinavian Ice Sheet: from MIS 4 to the end of the Last Glacial Maximum. Boreas 39, 410–435. Hughes, A. L. C., Gyllenkreutz, R., Lohne, Ø. S., Mangerud, J. & Svendsen, J. I. The last Eurasian ice sheets – a chronological database and time-slice reconstruction, DATED-1. Boreas 45. 10.1111/bor.12142 . ISSN 0300–9483 (2016). Grant, K. M. et al . Rapid coupling between ice volume and polar temperature over the past 150,000 years. Nature 491, 744–747. doi: 10.1038/nature11593 (2012). Buffett, B. & Archer, D. Global inventory of methane clathrate: sensitivity to changes in the deep ocean. Earth Planet. Sci. Lett. 227, 185–199 (2004). Desbruyère, D. G., Purkey, S. G., McDonagh, E. L., Johnson, G. C. & King, B. A. Deep and abyssal ocean warming from 35 years of repeat hydrography. Geophys. Res. Lett. 43, 10,356–10,365. doi: 10.1002/2016GL070413 (2016). Messias, M, -J. & Mercier, H. The redistribution of anthropogenic excess heat is a key driver of warming in the North Atlantic. Comm. Earth & Environ. 3, 118. https://doi.org/10.1038/s43247-022-00443-4 (2022). Juggins, S. C2 Version 1.5 User guide. Software for Ecological and Palaeoecological Data Analysis and Visualization . Newcastle University (2007). Duplessy, J. -C., Moyes, J. & Pujol, C. Deep water formation in the North Atlantic Ocean during the last ice age. Nature 286, 479–482 (1980). Shackleton, N. J. Attainment of isotopic equilibrium between ocean water and the benthonic foraminifera genus Uvigerina : isotopic changes in the ocean during the last glacial. Colloques Internationaux du C.N.R.S. 219, 203–209 (1974). Heaton, T. J. et al . Marine20 - the marine radiocarbon age calibration curve (0–55,000 cal BP). Radiocarbon 62, 779–820, doi: 10.1017/RDC.2020.68 (2020). Blaauw, M. & Christen, J. A. Flexible paleoclimate age-depth models using an autoregressive gamma process. Bayesian Anal. 6, 457–474. doi: 10.1214/11-BA618 (2011). Locarnini, R. A. et al . World Ocean Atlas 2018. In A. Mishonov Technical (Ed.), NOAA Atlas NESDIS 81 (Volume 1: Temperature, p. 52) (2018). Tables Table 1 is available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table1.xlsx Rasmussenetal.Supplementaryinformation.pdf Cite Share Download PDF Status: Published Journal Publication published 27 Sep, 2024 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 21 May, 2024 Reviews received at journal 04 May, 2024 Reviews received at journal 01 May, 2024 Reviews received at journal 13 Apr, 2024 Reviewers agreed at journal 09 Apr, 2024 Reviewers agreed at journal 09 Apr, 2024 Reviewers agreed at journal 08 Apr, 2024 Reviewers invited by journal 07 Apr, 2024 Editor assigned by journal 02 Apr, 2024 Editor invited by journal 02 Apr, 2024 Submission checks completed at journal 02 Apr, 2024 First submitted to journal 22 Mar, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-4149143\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":287207847,\"identity\":\"1f742e5d-e037-44d1-9b90-6444e5147b07\",\"order_by\":0,\"name\":\"Tine L. Rasmussen\",\"email\":\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA20lEQVRIiWNgGAWjYDACZlSuDQMbIR08aFrSGNgI6eFB4x9mIGiNPTvvwQeMe+zsdWekP/7wccf5xD75BrYHH/A6jC/ZgOFZcuK2GzlmkjPP3E5sY2NgN5yBVwuPmQTDAeYEsxs5bMy8bWAtbNLo7kXTYv6D4UC9vdmN9Mef/7adI0qLGQPDgcOM224kGEgzth0gQsthHmOJhAPHE7edeWMm2duWbNzGltgmic8v7P1nDD98OFBtb3YcGGI/2+xk5zcfPiaBL8TAIAGVy9hASMMoGAWjYBSMAgIAAGw0RFMD7aohAAAAAElFTkSuQmCC\",\"orcid\":\"\",\"institution\":\"UiT the Arctic University of Norway\",\"correspondingAuthor\":true,\"prefix\":\"\",\"firstName\":\"Tine\",\"middleName\":\"L.\",\"lastName\":\"Rasmussen\",\"suffix\":\"\"},{\"id\":287207848,\"identity\":\"1186c61e-3e12-46e3-afc3-28d40ff1c696\",\"order_by\":1,\"name\":\"Naima El bani Altuna\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"UiT the Arctic University of Norway\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Naima\",\"middleName\":\"El bani\",\"lastName\":\"Altuna\",\"suffix\":\"\"},{\"id\":287207849,\"identity\":\"a6de7ed8-3038-452d-901d-3a64693a0c0d\",\"order_by\":2,\"name\":\"Erik Thomsen\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Erik\",\"middleName\":\"\",\"lastName\":\"Thomsen\",\"suffix\":\"\"}],\"badges\":[],\"createdAt\":\"2024-03-22 10:53:54\",\"currentVersionCode\":1,\"declarations\":\"\",\"doi\":\"10.21203/rs.3.rs-4149143/v1\",\"doiUrl\":\"https://doi.org/10.21203/rs.3.rs-4149143/v1\",\"draftVersion\":[],\"editorialEvents\":[{\"content\":\"https://doi.org/10.1038/s41598-024-72865-3\",\"type\":\"published\",\"date\":\"2024-09-27T15:57:22+00:00\"}],\"editorialNote\":\"\",\"failedWorkflow\":false,\"files\":[{\"id\":54186407,\"identity\":\"8bf35480-f196-4447-a32a-d8016a478cac\",\"added_by\":\"auto\",\"created_at\":\"2024-04-05 18:19:44\",\"extension\":\"jpg\",\"order_by\":1,\"title\":\"Figure 1\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":352449,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eMajor currents and bathymetry of the study area. a\\u003c/strong\\u003e Map of Nordic Seas with major currents indicated showing location of studied core HH12-940PC (79.08 °N, 05.36 °E, 1294 m water depth) (white circle) from western Vestnesa Ridge, published core PS62/015-3 from Denmark Strait (black circle)\\u003csup\\u003e34\\u003c/sup\\u003e and Nyegga pockmark area with published records (black frame)\\u003csup\\u003e35\\u003c/sup\\u003e. Map with mean annual sea surface temperature for the 2005–2017 period\\u003csup\\u003e85\\u003c/sup\\u003e modified from ref. 12. \\u003cstrong\\u003eb\\u003c/strong\\u003e Bathymetric map of western Vestnesa Ridge showing positions of core HH12-940PC (white dot) and of published records discussed in the text; core HH15-1252PC from non-seep conditions north of the ridge\\u003csup\\u003e12\\u003c/sup\\u003e, and core HH12-930GC (black dots), and multicore MUC 12 (black open circle) from eastern Vestnesa Ridge\\u003csup\\u003e50,57\\u003c/sup\\u003e. White frame marks the western inactive, and black frame, the eastern active pockmark field. Abbreviations: NwAC = Norwegian Atlantic Current; IC = Irminger Current; WSC = West Spitsbergen Current; EGC = East Greenland Current; ESC = East Spitsbergen Current.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig1.jpg\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4149143/v1/6401e53b954fc1dde36b1d9e.jpg\"},{\"id\":54186405,\"identity\":\"2e7dc69a-2d5e-4727-8133-01d82b141c1c\",\"added_by\":\"auto\",\"created_at\":\"2024-04-05 18:19:44\",\"extension\":\"jpg\",\"order_by\":2,\"title\":\"Figure 2\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":546327,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eAge-depth plot, correlation to NGRIP ice core GICC05 age and sedimentation rates of core HH12-940PC\\u003c/strong\\u003e. \\u003cstrong\\u003ea\\u003c/strong\\u003e Age-depth plot based on calibrated AMS-\\u003csup\\u003e14\\u003c/sup\\u003eC dates using Bayesian modeling showing probability ranges for each date (see text for explanation and Table 1). \\u003cstrong\\u003eb\\u003c/strong\\u003e Age-depth plot based on correlation with the NGRIP GICC05 time scale (b2k = before 2 ka)\\u003csup\\u003e14\\u003c/sup\\u003e (black squares) plotted together with calibrated ages (red dots). Outlier dates are marked by red circles. \\u003cstrong\\u003ec \\u003c/strong\\u003eSedimentation rates (cm/ka) calculated based on correlation points to the ice core.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig2.jpg\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4149143/v1/fa1ddd2d1339fcaea138e7d1.jpg\"},{\"id\":54186404,\"identity\":\"fe03d44f-22a4-443c-bf4a-faf3857b800c\",\"added_by\":\"auto\",\"created_at\":\"2024-04-05 18:19:44\",\"extension\":\"jpg\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":597148,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eSelected records from core HH12-940PC\\u003c/strong\\u003e. \\u003cstrong\\u003ea\\u003c/strong\\u003e Planktic δ\\u003csup\\u003e18\\u003c/sup\\u003eO measured in the foraminiferal species \\u003cem\\u003eNeogloboquadrina pachyderma\\u003c/em\\u003e (N. pach.). \\u003cstrong\\u003eb\\u003c/strong\\u003e Corrected (see Methods) benthic δ\\u003csup\\u003e18\\u003c/sup\\u003eO measured in \\u003cem\\u003eCibicidoides wuellerstorfi\\u003c/em\\u003e (blue squares), \\u003cem\\u003eMelonis barleeanus\\u003c/em\\u003e (red squares) and \\u003cem\\u003eCassidulina neoteretis \\u003c/em\\u003e(black squares). \\u003cstrong\\u003ec\\u003c/strong\\u003e Planktic δ\\u003csup\\u003e13\\u003c/sup\\u003eC measured in \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e (N. pach.). Vertical grey bar indicates typical range of glacial and interglacial values. \\u003cstrong\\u003ed\\u003c/strong\\u003e Benthic δ\\u003csup\\u003e13\\u003c/sup\\u003eC measured in \\u003cem\\u003eC. wuellerstorfi\\u003c/em\\u003e (blue squares), \\u003cem\\u003eM. barleeanus\\u003c/em\\u003e (red squares) and \\u003cem\\u003eC. neoteretis \\u003c/em\\u003e(black squares). Vertical grey bar indicates typical range of glacial and interglacial values (see text for explanation). \\u003cstrong\\u003ee\\u003c/strong\\u003e Percentage distribution of polar planktic foraminiferal species \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e (note inverse scale) with position of calibrated AMS-\\u003csup\\u003e14\\u003c/sup\\u003eC dates indicated, asterisks mark outlier dates (see Table 1). \\u003cstrong\\u003ef\\u003c/strong\\u003e Percentage of epifaunal benthic species \\u003cem\\u003eC. wuellerstorfi\\u003c/em\\u003e. \\u003cstrong\\u003eg \\u003c/strong\\u003ePercentage of shallow infaunal benthic species \\u003cem\\u003eC. neoteretis\\u003c/em\\u003e. Corelog shown to the right of (\\u003cstrong\\u003eg\\u003c/strong\\u003e). Abbreviations: YD = Younger Dryas; LGM = Last Glacial Maximum; H = Heinrich stadial; MIS = Marine Isotope Stage. Blue bars mark Heinrich stadials.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig3.jpg\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4149143/v1/a76d636e176de969e61d7890.jpg\"},{\"id\":54186410,\"identity\":\"2a7af5d1-2a70-4269-9cd2-5da8a42a46df\",\"added_by\":\"auto\",\"created_at\":\"2024-04-05 18:19:45\",\"extension\":\"jpg\",\"order_by\":4,\"title\":\"Figure 4\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":596873,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eDetails of core HH12-940PC for the lower 545–838 cm (MIS 3 and MIS 2)\\u003c/strong\\u003e. \\u003cstrong\\u003ea \\u003c/strong\\u003ePercentage distribution of polar planktic foraminiferal species \\u003cem\\u003eNeogloboquadrina pachyderma\\u003c/em\\u003e (N. pach.; note inverse scale). \\u003cstrong\\u003eb \\u003c/strong\\u003eAbsolute bottom water temperatures (BWT) calculated from transfer functions of the benthic foraminiferal faunas in the core. \\u003cstrong\\u003ec \\u003c/strong\\u003eConcentration of calcareous nodules \\u0026gt;0.5 mm from authigenic carbonate precipitation (see text for explanation) in number per gram dry weight sediment. Position of layers of chemosymbiotic bivalves and gastropods are indicated (see legend below). \\u003cstrong\\u003ed \\u003c/strong\\u003eCorrected benthic δ\\u003csup\\u003e18\\u003c/sup\\u003eO measured in \\u003cem\\u003eMelonis barleeanus\\u003c/em\\u003e and \\u003cem\\u003eCassidulina neoteretis\\u003c/em\\u003e. Light blue squares are δ\\u003csup\\u003e18\\u003c/sup\\u003eO measured in authigenic carbonate nodules (see text for explanation) with values indicated. \\u003cstrong\\u003ee \\u003c/strong\\u003eBenthic δ\\u003csup\\u003e13\\u003c/sup\\u003eC measured in \\u003cem\\u003eM. barleeanus\\u003c/em\\u003e and \\u003cem\\u003eC. neoteretis\\u003c/em\\u003e. Vertical grey bar indicates typical range of glacial and interglacial values. Light blue squares are δ\\u003csup\\u003e13\\u003c/sup\\u003eC measured in authigenic carbonate nodules (see text for explanation) with values indicated. Vertical black bars show intervals with too few pristine shells for isotope analysis. To the right are shown NGRIP Ice Core δ\\u003csup\\u003e18\\u003c/sup\\u003eO data versus SMOW\\u003csup\\u003e14\\u003c/sup\\u003e. Note break in y-axis for LGM interval 21–17 ka. Heinrich stadials H5 to H1, stadial (S) and interstadial numbers 12–2 are indicated. Blue horizontal bars mark Heinrich stadials, grey bars stadials. Black oblique lines mark Bond cycle configurations in panel \\u003cstrong\\u003ee\\u003c/strong\\u003e and in ice core record (note few data points in interstadial 8 in core 940, because of too few pristine foraminiferal specimens available for analysis (severe coatings of shells with authigenic carbonate)).\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig4.jpg\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4149143/v1/c366897bfdb3e39c654ca891.jpg\"},{\"id\":54186408,\"identity\":\"0bf54557-80ab-434b-bd84-9f552c501a4b\",\"added_by\":\"auto\",\"created_at\":\"2024-04-05 18:19:44\",\"extension\":\"jpg\",\"order_by\":5,\"title\":\"Figure 5\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":691862,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eDistribution of bottom water temperatures, dominant benthic foraminiferal species and correlation between cores HH12-940PC (a–e) and HH15-1252PC\\u003c/strong\\u003e\\u003csup\\u003e\\u003cstrong\\u003e26 \\u003c/strong\\u003e\\u003c/sup\\u003e\\u003cstrong\\u003e(f–k) for MIS 3 and MIS 2\\u003c/strong\\u003e. Core \\u003cstrong\\u003eHH12-940PC (a–e): a \\u003c/strong\\u003eBottom water temperatures (BWT) calculated from transfer functions (TF) of the benthic foraminiferal faunas. \\u003cstrong\\u003eb\\u003c/strong\\u003e Percentage of \\u003cem\\u003eCassidulina neoteretis\\u003c/em\\u003e. \\u003cstrong\\u003ec\\u003c/strong\\u003e percentage of \\u003cem\\u003eMelonis barleeanus\\u003c/em\\u003e. \\u003cstrong\\u003ed\\u003c/strong\\u003e Percentage of \\u003cem\\u003eCassidulina reniforme\\u003c/em\\u003e. \\u003cstrong\\u003ee \\u003c/strong\\u003ePercentage of Atlantic species (ATL) (see text for explanation and Table S1).\\u003cstrong\\u003e Core HH15-1252PC\\u003c/strong\\u003e\\u003csup\\u003e\\u003cstrong\\u003e \\u003c/strong\\u003e\\u003c/sup\\u003e\\u003cstrong\\u003e(f–k): f\\u003c/strong\\u003e Bottom water temperatures (BWT) from measurements of Mg/Ca. \\u003cstrong\\u003eg\\u003c/strong\\u003e Percentage of \\u003cem\\u003eCassidulina neoteretis\\u003c/em\\u003e. \\u003cstrong\\u003eh\\u003c/strong\\u003e percentage of \\u003cem\\u003eMelonis barleeanus\\u003c/em\\u003e. \\u003cstrong\\u003ei\\u003c/strong\\u003e Percentage of \\u003cem\\u003eCassidulina reniforme\\u003c/em\\u003e. \\u003cstrong\\u003ej \\u003c/strong\\u003ePercentage of Atlantic species (ATL) (see text for explanation and Table S1).\\u003cstrong\\u003e k\\u003c/strong\\u003e Benthic δ\\u003csup\\u003e13\\u003c/sup\\u003eC measured in \\u003cem\\u003eC. neoteretis\\u003c/em\\u003e. Heinrich stadials H5 to H1 and stadial (S) and interstadial numbers 12–2 are indicated. Blue horizontal bars mark Heinrich stadials, grey bars stadials.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig5.jpg\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4149143/v1/dd7796a65fa71bbf0a82beea.jpg\"},{\"id\":54186646,\"identity\":\"194f72c2-9fb0-4761-8c6b-68d1f7490190\",\"added_by\":\"auto\",\"created_at\":\"2024-04-05 18:27:44\",\"extension\":\"jpg\",\"order_by\":6,\"title\":\"Figure 6\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":384085,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eHistogram plot of bottom water temperature increases and rates. \\u003c/strong\\u003eTemperature increases calculated from the end of an interstadial to the maximum obtained in the subsequent stadial/Heinrich event for cores HH12-940PC (left) and HH15-1252PC (right) (blue bars) and the calculated rate of the temperature increases (red bars) are shown. The red line shows the average value for the calculated variable. Heinrich events H5 to H1 and stadial (S) and interstadial (IS) numbers 13–2 are indicated. Black oblique lines mark Bond cycle configurations.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig6.jpg\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4149143/v1/3f2b64bd2a86586be533e691.jpg\"},{\"id\":65627187,\"identity\":\"9dce7136-ebbf-4d6f-9a43-1254f9e8e2db\",\"added_by\":\"auto\",\"created_at\":\"2024-09-30 16:13:07\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":4093217,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4149143/v1/9d1dc624-9928-4040-8593-a442bec1989b.pdf\"},{\"id\":54186645,\"identity\":\"e26f618b-dd48-42b4-9df1-9ec229b7d719\",\"added_by\":\"auto\",\"created_at\":\"2024-04-05 18:27:44\",\"extension\":\"xlsx\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":12037,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"Table1.xlsx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4149143/v1/a479f1bc99e84b718262ae8f.xlsx\"},{\"id\":54186411,\"identity\":\"61ca7d7d-1096-4c54-8b20-2c0262786abe\",\"added_by\":\"auto\",\"created_at\":\"2024-04-05 18:19:45\",\"extension\":\"pdf\",\"order_by\":9,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":1059375,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"Rasmussenetal.Supplementaryinformation.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4149143/v1/b701797fb4797df8110f4da4.pdf\"}],\"financialInterests\":\"No competing interests reported.\",\"formattedTitle\":\"Variations in deep-sea methane seepage linked to millennial-scale changes in bottom water temperatures ~50–6 ka, NW Svalbard margin\",\"fulltext\":[{\"header\":\"Introduction\",\"content\":\"\\u003cp\\u003eNumerous studies have shown that the northern North Atlantic including the Nordic Seas and Svalbard margin during the last glaciation, 50\\u0026ndash;12 ka, was affected by twelve abrupt temperature fluctuations\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR2 CR3 CR4 CR5 CR6 CR7 CR8 CR9 CR10 CR11 CR12\\\" citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003e, which correlate closely with the millennial timescale Dansgaard-Oeschger (DO) events in the Greenland ice cores\\u003csup\\u003e\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e15\\u003c/span\\u003e\\u003c/sup\\u003e. The DO events of cold stadials to warm interstadials reflect a series of abrupt warmings over Greenland of up to 16\\u0026deg;C\\u003csup\\u003e\\u003cspan citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e16\\u003c/span\\u003e\\u003c/sup\\u003e. The main cause for the DO-events is repeated reversals of the Atlantic Meridional Ocean Circulation (AMOC)\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR17\\\" class=\\\"CitationRef\\\"\\u003e17\\u003c/span\\u003e\\u003c/sup\\u003e (see below). The abrupt changes related to the DO events affected both the surface and the bottom water temperatures (BWT). During the glacial period BWT reached 5 to 5.5\\u0026deg;C at 1200 to 1300 m water depth in in the Norwegian and Greenland Sea, respectively\\u003csup\\u003e\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e\\u003c/sup\\u003e, which is close to 6\\u0026deg;C above present day temperatures.\\u003c/p\\u003e \\u003cp\\u003eMethane, a powerful greenhouse gas, is presently released into the oceans from gas reservoirs located deep in the sediments on the continental margin. Most of the gas is trapped in ice in the Gas Hydrate Stability Zone (GHSZ) and kept stable by the high pressure and low temperature\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003e. The GHSZ on the slopes can be several hundred meters thick and hosts vast amounts of gas hydrates\\u003csup\\u003e\\u003cspan citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e19\\u003c/span\\u003e\\u003c/sup\\u003e. High concentrations of gas hydrates generally occur deep in the sediments depending on the presence of sediments of high porosity\\u003csup\\u003e\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e\\u003c/sup\\u003e. Facilitated by faults and porous sediments, free and dissolved gas in the pore water can migrate upward through the GHSZ and through overlying sediments with the potential to reach the atmosphere\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR22\\\" citationid=\\\"CR21\\\" class=\\\"CitationRef\\\"\\u003e21\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e23\\u003c/span\\u003e\\u003c/sup\\u003e. Growing concern about the effect of greenhouse gases on the global warming, rising surface and deep ocean temperatures and on the increasing deep-ocean acidification\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR25\\\" citationid=\\\"CR24\\\" class=\\\"CitationRef\\\"\\u003e24\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR26\\\" class=\\\"CitationRef\\\"\\u003e26\\u003c/span\\u003e\\u003c/sup\\u003e has fostered an intensified interest on the future stability of the GHSZ in a warmer ocean\\u003csup\\u003e\\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e23\\u003c/span\\u003e,\\u003cspan additionalcitationids=\\\"CR28 CR29 CR30\\\" citationid=\\\"CR27\\\" class=\\\"CitationRef\\\"\\u003e27\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR31\\\" class=\\\"CitationRef\\\"\\u003e31\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003eSeveral studies indicate that there is an overall correlation between variations in BWT and the intensity of the methane leaks\\u003csup\\u003e\\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e23\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR29\\\" class=\\\"CitationRef\\\"\\u003e29\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR32\\\" class=\\\"CitationRef\\\"\\u003e32\\u003c/span\\u003e\\u003c/sup\\u003e. Many other explanations have been suggested, viz., changes in hydrostatic pressure (sea level), tectonic activity/isostatic rebound, and sediment loading. However, concrete data from deep ocean sites are few\\u003csup\\u003e\\u003cspan citationid=\\\"CR31\\\" class=\\\"CitationRef\\\"\\u003e31\\u003c/span\\u003e,\\u003cspan additionalcitationids=\\\"CR34\\\" citationid=\\\"CR33\\\" class=\\\"CitationRef\\\"\\u003e33\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR35\\\" class=\\\"CitationRef\\\"\\u003e35\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003eIn the present study we have reconstructed temperature fluctuations in a core from 1300 m water depth at Vestnesa Ridge on the northwestern margin of Svalbard margin covering the time-period\\u0026thinsp;~\\u0026thinsp;50\\u0026ndash;6 ka. The purpose of the study was to investigate if there is a connection between BWT and the seepage of methane from the seafloor. The locality was selected because it represents a poorly known deep-water environment and more importantly, it includes the most unstable period of the last glaciation, 50\\u0026ndash;12 ka. This permits us to examine and compare gas hydrate stability during several warming and cooling events. Furthermore, the close connection between the oceanographic fluctuations in the North Atlantic and the temperature oscillations recorded in Greenland ice cores allows us to obtain a high degree of precision in the correlation of individual events.\\u003c/p\\u003e \\u003cp\\u003eThe study is based on 230 samples from marine core HH12-940PC (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ea,b). The study comprises records of relative and absolute abundance of planktic and benthic foraminiferal species, concentration of ice rafted debris (IRD), planktic and benthic carbon and oxygen isotopes (δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC and δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO), and BWT calculated by transfer functions of the benthic foraminiferal census data. The general stratigraphy of the core was established based on fourteen AMS-\\u003csup\\u003e\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e\\u003c/sup\\u003eC dates and correlation to individual DO events in the Greenland NGRIP ice core. The reconstruction of changes in strength of methane seepage is based on carbon isotopes combined with foraminiferal and macrofaunal census data (chemosymbiotic bivalves). Carbonate nodules from authigenic precipitation of carbonates from methane seepage were also quantified and measured for carbon and oxygen isotopes.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eMillennial-scale temperature fluctuations in the Svalbard Margin.\\u003c/b\\u003e Bottom water temperature changes on the western Svalbard margin from ~\\u0026thinsp;50 to 12 ka are closely linked to the millennial time-scale climatic and oceanographic fluctuations that characterizes the North Atlantic region during the last glaciation\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u003c/sup\\u003e. These fluctuations are well documented in the Greenland ice cores as well as in North Atlantic sediment cores and a precise correlation between the two systems has been established\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR2 CR3 CR4 CR5 CR6 CR7 CR8 CR9 CR10 CR11 CR12 CR13 CR14\\\" citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e15\\u003c/span\\u003e\\u003c/sup\\u003e. This allows us to transfer the naming, numbering, and configuration of the DO events in the Greenland ice cores to the sediment cores of Vestnesa Ridge, including the warm interstadial events and the cold stadial events.\\u003c/p\\u003e \\u003cp\\u003eIn the marine records the stadials are defined by low benthic and planktic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values, high content of ice rafted debris (IRD), and dominance of the polar planktic foraminiferal species \\u003cem\\u003eNeogloboquadrina pachyderma\\u003c/em\\u003e\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u003c/sup\\u003e. The warm interstadials are defined by high benthic and planktic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values, no or low IRD content, and low percentage of \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u003c/sup\\u003e. Particularly cold and long lasting stadials in the marine records are termed Heinrich stadials (H). They mark prolonged IRD- events of icebergs released from the Laurentide Ice Sheet at 6\\u0026ndash;10 ka intervals referred to as \\u0026lsquo;Bond\\u0026rsquo; cycles\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003eThe causes for the millennial-scale fluctuations are generally attributed to instabilities in the strength and mode of the AMOC. Today, warm Atlantic Water of the Norwegian-Atlantic Current flows into the Nordic Seas at the surface (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ea). It is cooled in winter and convects to form cold deep and intermediate water overflowing the Greenland-Scotland Ridge contributing to North Atlantic Deep Water\\u003csup\\u003e\\u003cspan citationid=\\\"CR17\\\" class=\\\"CitationRef\\\"\\u003e17\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ea). During the cold periods (stadials and Heinrich stadials) of the glacial period, the sea surface of the Nordic Seas and North Atlantic was covered by sea ice and icebergs and deep convection stopped\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR3\\\" citationid=\\\"CR2\\\" class=\\\"CitationRef\\\"\\u003e2\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR17\\\" class=\\\"CitationRef\\\"\\u003e17\\u003c/span\\u003e\\u003c/sup\\u003e. However, below the cold sea surface, Atlantic water continued to flow into the North Atlantic and Nordic Seas here warming the intermediate and upper deep-water masses. The natural cold surface conditions were interrupted by abrupt warmings during which the oceanic circulation pattern reversed allowing warm Atlantic water to enter the North Atlantic and Nordic Seas at the surface (interstadials). In the Nordic Seas, deep convection was abruptly reestablished causing a renewed cooling of the intermediate and deeper water.\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eStudy area.\\u003c/b\\u003e Vestnesa Ridge is a southeast-northwest oriented ridge (05\\u0026ndash;08 \\u0026deg;E) located at 79 \\u0026deg;N at water depth between 1200 m to the east and \\u0026gt;\\u0026thinsp;1300 m to the west (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003eb). The ridge is in direct contact with cold intermediate water (-0.5\\u0026deg;C) generated by the convection in the Nordic Seas\\u003csup\\u003e\\u003cspan citationid=\\\"CR36\\\" class=\\\"CitationRef\\\"\\u003e36\\u003c/span\\u003e\\u003c/sup\\u003e. The ridge is covered by thick contourite sediments, where core HH12-940PC was taken (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003eb).\\u003c/p\\u003e \\u003cp\\u003eThe crest of the ridge is marked by a series of pockmarks which at 1200 m water depth at the eastern part show intense seepage of methane\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR38\\\" citationid=\\\"CR37\\\" class=\\\"CitationRef\\\"\\u003e37\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR39\\\" class=\\\"CitationRef\\\"\\u003e39\\u003c/span\\u003e\\u003c/sup\\u003e. The gas migrates upwards from a deep thermogenic reservoir through faulted chimneys below the pockmarks, and gas flares rise more than 800 m from the seafloor\\u003csup\\u003e\\u003cspan citationid=\\\"CR38\\\" class=\\\"CitationRef\\\"\\u003e38\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR40\\\" class=\\\"CitationRef\\\"\\u003e40\\u003c/span\\u003e\\u003c/sup\\u003e. The western part is apparently less active as indicated by the presence of several inactive pockmarks with no visible flares\\u003csup\\u003e\\u003cspan citationid=\\\"CR39\\\" class=\\\"CitationRef\\\"\\u003e39\\u003c/span\\u003e\\u003c/sup\\u003e. The base of the GHSZ is located\\u0026thinsp;~\\u0026thinsp;160\\u0026ndash;180 m below the sediment surface\\u003csup\\u003e\\u003cspan citationid=\\\"CR39\\\" class=\\\"CitationRef\\\"\\u003e39\\u003c/span\\u003e\\u003c/sup\\u003e. The GHSZ is several hundred meters thick\\u003csup\\u003e\\u003cspan citationid=\\\"CR41\\\" class=\\\"CitationRef\\\"\\u003e41\\u003c/span\\u003e\\u003c/sup\\u003e and gas hydrates have been found up to a few meters below the sediment surface in some of the active pockmarks in the eastern part\\u003csup\\u003e\\u003cspan citationid=\\\"CR40\\\" class=\\\"CitationRef\\\"\\u003e40\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR42\\\" class=\\\"CitationRef\\\"\\u003e42\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR43\\\" class=\\\"CitationRef\\\"\\u003e43\\u003c/span\\u003e\\u003c/sup\\u003e. The sulfate-methane transition zone (SMTZ) designating the transition of anaerobic oxidation of methane by archaea and sulfate-reducing bacteria\\u003csup\\u003e\\u003cspan citationid=\\\"CR44\\\" class=\\\"CitationRef\\\"\\u003e44\\u003c/span\\u003e\\u003c/sup\\u003e is located\\u0026thinsp;\\u0026gt;\\u0026thinsp;2\\u0026ndash;~10 m below present sediment surface on the western inactive part indicating little or no seepage\\u003csup\\u003e\\u003cspan citationid=\\\"CR42\\\" class=\\\"CitationRef\\\"\\u003e42\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003eCore HH12-940PC was taken from a sediment-filled pockmark at 1294 m water depth from the western part of Vestnesa Ridge (79.08 \\u0026deg;N, 05.36 \\u0026deg;E) (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e) (from here on termed core 940). This part of the ridge was active in the past, but is presently inactive\\u003csup\\u003e\\u003cspan citationid=\\\"CR37\\\" class=\\\"CitationRef\\\"\\u003e37\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR39\\\" class=\\\"CitationRef\\\"\\u003e39\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR45\\\" class=\\\"CitationRef\\\"\\u003e45\\u003c/span\\u003e\\u003c/sup\\u003e. To test our results, we compare the records from core 940, with records from nearby core HH15-1252PC taken north of Vestnesa Ridge (from here on termed core 1252), which has been unaffected by seepage of methane\\u003csup\\u003e\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003eb). Core 1252 covers the same period as core 940. It furthermore comprises a quantification of BWT based on the Mg/Ca ratio of benthic forminifera. The sediments at both core sites consist mainly of fine-grained hemipelagic mud and clayey silts.\\u003c/p\\u003e\"},{\"header\":\"Results\",\"content\":\"\\u003cp\\u003eTwelve out of 14 AMS-\\u003csup\\u003e\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e\\u003c/sup\\u003eC dates are in chronological order (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e; Table\\u0026nbsp;1; Figs. S1\\u0026ndash;S2). With eight species of planktic and more than 100 species of benthic foraminifera (Table \\u003cspan refid=\\\"MOESM1\\\" class=\\\"InternalRef\\\"\\u003eS1\\u003c/span\\u003e), the overall diversity of the benthic foraminiferal faunas is quite high (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e\\u0026ndash;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e). During most stadial intervals several benthic species of boreal to subtropical affinity termed the Atlantic Species Group, appears\\u003csup\\u003e\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR46\\\" class=\\\"CitationRef\\\"\\u003e46\\u003c/span\\u003e\\u003c/sup\\u003e (see Methods; Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e; Figs. S3, S4).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eStratigraphy and identification of Dansgaard-Oeschger events.\\u003c/b\\u003e The AMS-\\u003csup\\u003e\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e\\u003c/sup\\u003eC dates in combination with the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO record indicate that the core comprises the mid-late part of marine isotope stage (MIS) 3, the whole of MIS 2 and the early part of MIS 1 (mid-late Weichselian to mid Holocene) (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea,b). Based on the lowermost two dates and assuming linear sedimentation rate, the oldest sediments of the core are calculated to ~\\u0026thinsp;50 ka (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e). Similarly, from the uppermost two dates, the youngest sediments are calculated to ~\\u0026thinsp;6.3 ka.\\u003c/p\\u003e \\u003cp\\u003eThe lower part of the core from 838 to 630 cm is referred to MIS 3 (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e, \\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e). This interval shows high variability of most parameters including stable isotopes (δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO and δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC; Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e), BWT, the percentages of the dominating planktic and benthic species \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e, \\u003cem\\u003eCassidulina neoteretis\\u003c/em\\u003e, \\u003cem\\u003eMelonis barleeanus\\u003c/em\\u003e, and \\u003cem\\u003eCassidulina reniforme\\u003c/em\\u003e and BWT (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ee, \\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ea,b, \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e; see also Supplementary text). A similar pattern is seen in core 1252 north of Vestnesa Ridge (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e; Fig. S4). Stadials are identified by low planktic and benthic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO, high content of IRD, and dominance of the polar planktic species \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e. Interstadials are identified by high δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO, no/low IRD and lower percentages of \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e. The BWT in MIS 3 shifts between low temperatures during the interstadials and high temperatures during the stadials (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003eb, \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ea,f). The composition of the benthic foraminiferal faunas shows that the interstadials are dominated by \\u003cem\\u003eM. barleeanus\\u003c/em\\u003e, \\u003cem\\u003eNonionella\\u003c/em\\u003e spp., \\u003cem\\u003eStainforthia\\u003c/em\\u003e spp., and \\u003cem\\u003eC. reniforme\\u003c/em\\u003e, whereas the stadials are dominated by \\u003cem\\u003eC. neoteretis\\u003c/em\\u003e and/or the Atlantic Species Group (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e; Fig. S4). The changes in relative abundance of the planktic species \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e is typical for the Nordic Seas where it reflects shifts in influence of cold polar surface water, and warm Atlantic water\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR2 CR3\\\" citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR6\\\" class=\\\"CitationRef\\\"\\u003e6\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ea).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eThe variability encountered in core 940 is characteristic for mid-late MIS 3 and MIS 2 in the Nordic Seas and North Atlantic and it allows us to identify Heinrich stadials H5, H4 and H3 as well as DO events 12\\u0026ndash;5 of MIS 3\\u003csup\\u003e1\\u0026ndash;9,12,14\\u0026ndash;16\\u003c/sup\\u003e. Our identification to specific DO events is confirmed by correlation of core 940 to the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO record of the NGRIP ice core where these events are defined and dated. Furthermore, the stratigraphy of core 940 is quite similar to that of nearby core 1252\\u003csup\\u003e12\\u003c/sup\\u003e (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb, \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e; Figs. S3, S4) (see Methods).\\u003c/p\\u003e \\u003cp\\u003eThe early part of MIS 2 is very compressed with low sedimentation rates (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ec). We can, nevertheless, recognize interstadials 4, 3 and 2, plus H2, the last glacial maximum (LGM) and H1 (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e\\u0026ndash;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e). The LGM comprises the core section from 585.5\\u0026ndash;570.5 cm, where it is recognized by the very high planktic and benthic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values. The LGM is dated to ~\\u0026thinsp;24.0\\u0026ndash;17.5 ka (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea,b) correlating well with the global isotope stack record\\u003csup\\u003e\\u003cspan citationid=\\\"CR47\\\" class=\\\"CitationRef\\\"\\u003e47\\u003c/span\\u003e\\u003c/sup\\u003e. The LGM is followed by H1 from 570.5\\u0026ndash;560.5 cm marking the beginning of the deglaciation dated to ~\\u0026thinsp;17.5\\u0026ndash;14.7 ka\\u003csup\\u003e\\u003cspan citationid=\\\"CR43\\\" class=\\\"CitationRef\\\"\\u003e43\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea,b). It is characterized by minima in the benthic and planktic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values and a high relative abundance of the Atlantic Species Group (\\u0026gt;\\u0026thinsp;12%) (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea,b, \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ee,j). The low δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values and the occurrence of the Atlantic Species Group is typical for H1 in the North Atlantic, Nordic Seas and Arctic Ocean\\u003csup\\u003e\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR46\\\" class=\\\"CitationRef\\\"\\u003e46\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003eThe warm interstadials B\\u0026oslash;lling and Aller\\u0026oslash;d 560.5\\u0026ndash;270.5 cm and dated to 14.7\\u0026ndash;~13.0 ka (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea,b, \\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e), show an expanded section and very high sedimentation rates with an average of 160 cm/ka as compared to 2 cm/ka for the LGM and H1 (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ec). The B\\u0026oslash;lling and Aller\\u0026oslash;d section appears quite disturbed with vertical channels/fractures (Fig. \\u003cspan refid=\\\"MOESM1\\\" class=\\\"InternalRef\\\"\\u003eS1\\u003c/span\\u003e; see discussion). The Younger Dryas cold stadial from 270.5\\u0026ndash;225.5 cm and dated to ~\\u0026thinsp;13.0\\u0026ndash;11.7 ka is distinguished by low planktic and benthic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e, \\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea,b). The Holocene interval from 225 cm to core top and dated to 11.7\\u0026ndash;6.3 ka (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e) is first of all distinguished by low percentages of the polar planktic species \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e and low planktic and benthic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea,b,e) and high concentrations of planktic and benthic foraminifera (Fig. S2d,e). The benthic foraminifera \\u003cem\\u003eC. wuellerstorfi\\u003c/em\\u003e is relative abundant in the Holocene part (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ef).\\u003c/p\\u003e \\u003cp\\u003eFurthermore, core 940 shows several distinct lithological features that clearly have stratigraphical value as they occur in numerous other records from the western Svalbard margin and always at the same stratigraphical position\\u003csup\\u003e\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR10\\\" class=\\\"CitationRef\\\"\\u003e10\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR40\\\" class=\\\"CitationRef\\\"\\u003e40\\u003c/span\\u003e\\u003c/sup\\u003e. These features comprise a debris flow/IRD deposit from the last glacial maximum dating\\u0026thinsp;~\\u0026thinsp;24.0 ka (582.5\\u0026ndash;575.5 cm down core), a laminated horizon deposited during the B\\u0026oslash;lling interstadial dating\\u0026thinsp;~\\u0026thinsp;14.5 ka (430\\u0026ndash;480 cm down core), and an early Holocene diatom layer dating\\u0026thinsp;~\\u0026thinsp;10.0 ka (175\\u0026ndash;180 cm down core) (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e; Fig. S2).\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eδ\\u003c/b\\u003e \\u003csup\\u003e \\u003cb\\u003e \\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e \\u003c/b\\u003e \\u003c/sup\\u003e \\u003cb\\u003eC and temperature variability in cores 940 and 1252.\\u003c/b\\u003e The δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values of marine organisms are strongly affected by methane in the environment. Tests of the majority of intermediate infaunal (\\u003cem\\u003eM. barleeanus\\u003c/em\\u003e) to shallow infaunal (\\u003cem\\u003eC. neoteretis\\u003c/em\\u003e) benthic foraminiferal species living in non-seep environments show interglacial values of δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC between \\u0026minus;\\u0026thinsp;1 and 0\\u0026permil;\\u003csup\\u003e48\\u003c/sup\\u003e and glacial values between \\u0026minus;\\u0026thinsp;2 and 0\\u0026permil;\\u003csup\\u003e12\\u003c/sup\\u003e. The epifaunal species \\u003cem\\u003eC. wuellerstorfi\\u003c/em\\u003e records glacial and interglacial values of 0 to \\u0026gt;\\u0026thinsp;+\\u0026thinsp;1\\u0026permil;\\u003csup\\u003e48\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ed). Values lower than about \\u0026minus;\\u0026thinsp;2\\u0026permil; are usually taken to indicate the presence of methane assuming that these foraminifera would obtain the low δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values either from the surrounding pore water or from consumed food\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR50\\\" citationid=\\\"CR49\\\" class=\\\"CitationRef\\\"\\u003e49\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR51\\\" class=\\\"CitationRef\\\"\\u003e51\\u003c/span\\u003e\\u003c/sup\\u003e. In the following descriptions, the \\u0026minus;\\u0026thinsp;2\\u0026ndash;0\\u0026permil; interval is termed the typical glacial-interglacial range for the infaunal species \\u003cem\\u003eC. neoteretis\\u003c/em\\u003e and \\u003cem\\u003eM. barleeanus\\u003c/em\\u003e combined and used as a visual guideline in the presentation (grey vertical bar in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ee).\\u003c/p\\u003e \\u003cp\\u003eComparison of the results of core 940 with previously published data from core 1252 covering the interval\\u0026thinsp;~\\u0026thinsp;50 to 12 ka, we find the same distribution of benthic and planktic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO, the same bottom water temperatures, and the same relative abundances of benthic foraminiferal species\\u003csup\\u003e\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e\\u003c/sup\\u003e. This allows a close correlation of the two records comprising H1\\u0026ndash;H5 and DO events 12\\u0026ndash;2 (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e, Figs. S3, S4). However. with respect to δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC the two sites are very different. In contrast to the fluctuating values of core 940 (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ee), all δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values of core 1252 are within the typical range of -2\\u0026ndash;0\\u0026permil; confirming that site 1252 was without any traces of methane seepage\\u003csup\\u003e\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ek). The lack of methane is further supported by the absence of carbonate nodules and chemosymbiotic mollusks, both common in core 940 (see discussion).\\u003c/p\\u003e \\u003cp\\u003eOne of the most conspicuous features of core 940 is the that the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC forms a pattern that mimic the pattern shown by the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO of the DO events in the Greenland ice cores with low values in the first interstadial above the Heinrich stadials and increasing values towards the next Heinrich stadial. The pattern corresponds to Bond-cycles\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u003c/sup\\u003e (see introduction) (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eThe lowest benthic values occur close to the stadial/interstadial boundaries - mostly at the beginning of the interstadials but sometimes at the end of the stadials (e.g., top of H5, S12 and H1; Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ee). From this low point the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values increase during the interstadial, but they generally remain below the typical range of -2\\u0026ndash;0\\u0026permil;. At the stadial boundary the values increase further and the values of the stadials are usually higher than the interstadial values and mostly above \\u0026minus;\\u0026thinsp;3\\u0026permil; (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ee). The Younger Dryas stadial show values above \\u0026minus;\\u0026thinsp;2\\u0026permil; (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ed). The planktic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC record of core 940 shows low values at the beginning of many interstadials, but not as consistently as in the benthic records. Moreover, it appears that several of the planktic minima occur slightly later than the benthic minima and are of much lower magnitude (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea\\u0026ndash;d).\\u003c/p\\u003e \\u003cp\\u003eIn core 940 many of the interstadials (though not all) display a high concentration of carbonate nodules (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ec; Fig. S2c). These nodules are characterized by very low δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values (-47.2 to -30.6\\u0026permil;; average \\u0026minus;\\u0026thinsp;41\\u0026permil;) and high δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values (5.7 to 7.2\\u0026permil;; average 6.7\\u0026permil;). Core 940 also contains layers rich in chemosymbiotic bivalves and other seep-associated macrofaunas. In addition to higher δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC (\\u0026gt;-3\\u0026permil;), these faunas co-occur with low benthic δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO and higher BWT (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e, \\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003eb\\u0026ndash;d, Fig. S2). They are found in relatively thin discrete layers in stadials S12 and S6 and in H5, H4, H3, H2 and H1 (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e). The chemosymbiotic faunas are absent from the interstadials just as they are absent from the non-seep core 1252\\u003csup\\u003e12\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003eIn core 940, the increase in bottom water temperature from interstadials to stadials varies from 1.2\\u0026deg;C between interstadial IS6 and stadial S6 to 4.7\\u0026deg;C between LGM and H1 (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003ea). In core 1252, the increases vary from 1.0\\u0026deg;C between IS7 and S7 to 5.7\\u0026deg;C between LGM to H1 (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003eb). For both cores, the temperature rises are largest in connection with the Heinrich stadials. The temperatures generally decrease successively in the subsequent stadials until the next Heinrich stadial, reflecting the pattern of the Bond cycles\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e). The calculated temperatures represent the maximum difference from the lowest temperature during the interstadials to the highest temperature during the subsequent stadial. The average rate of the temperature increases is 2.0\\u0026deg;C/ka (range 1.1\\u0026ndash;3.2\\u0026deg;C/ka) for core 940 and 1.9\\u0026deg;C/ka (range 1.4\\u0026ndash;2.5\\u0026deg;C/ka) for core 1252 (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003ea,b).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e\"},{\"header\":\"Discussion\",\"content\":\"\\u003cp\\u003e \\u003cb\\u003eDansgaard-Oeschger events and the emission of methane.\\u003c/b\\u003e The consistent millennial time-scale pattern shown by the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC events in core 940 strongly indicate that the events are not randomly distributed and that they are caused by a common forcing factor which varies concurrent with the DO oscillations. The most likely factor on the Vestnesa Ridge that fulfils these criteria is bottom water temperature which in the North Atlantic and Nordic Seas also fluctuates according to the DO events\\u003csup\\u003e\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan additionalcitationids=\\\"CR8\\\" citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR46\\\" class=\\\"CitationRef\\\"\\u003e46\\u003c/span\\u003e\\u003c/sup\\u003e. However, other factors such as tectonism/isostatic rebound, and hydrostatic pressure are also briefly discussed.\\u003c/p\\u003e \\u003cp\\u003eGlacial and interglacial δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values below the typical ranges of benthic foraminiferal species have generally been used to indicate the presence of methane\\u003csup\\u003e\\u003cspan citationid=\\\"CR49\\\" class=\\\"CitationRef\\\"\\u003e49\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR51\\\" class=\\\"CitationRef\\\"\\u003e51\\u003c/span\\u003e\\u003c/sup\\u003e. The immediate interpretation of the variation of δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC in core 940 is that the seepage of methane was low to moderate during the stadials where the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values generally are above ~-3\\u0026permil; (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ee). An abrupt decrease in δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC close to the stadial/interstadial transitions suggests that the seepage of methane at the beginning of the interstadials increased significantly. The peak was short-lasting, but the emission remained relatively high during the rest of the interstadials (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ee). Note that after ~\\u0026thinsp;10 ka in the Holocene high δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values in core 940 indicate a reduction or stop in seepage (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ec,d). Overall, it is important to note that the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values in core 940 are consistently lower than in core 1252 revealing that site 940 constantly was affected by methane also during the stadials (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ee, \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ek).\\u003c/p\\u003e \\u003cp\\u003eThe δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values of live benthic foraminiferal tests that have been exposed to methane generally range from 0 to -6 to -8\\u0026permil;, depending on species, indicating that the effect of methane on the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC in shells of foraminifera is relatively small\\u003csup\\u003e\\u003cspan citationid=\\\"CR34\\\" class=\\\"CitationRef\\\"\\u003e34\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR49\\\" class=\\\"CitationRef\\\"\\u003e49\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR50\\\" class=\\\"CitationRef\\\"\\u003e50\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR52\\\" class=\\\"CitationRef\\\"\\u003e52\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR53\\\" class=\\\"CitationRef\\\"\\u003e53\\u003c/span\\u003e\\u003c/sup\\u003e, This is especially evident when compared to the much lower values (-10\\u0026permil; to \\u0026lt;-20\\u0026permil;) measured in foraminiferal tests affected by authigenic carbonate\\u003csup\\u003e\\u003cspan citationid=\\\"CR40\\\" class=\\\"CitationRef\\\"\\u003e40\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR54\\\" class=\\\"CitationRef\\\"\\u003e54\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR55\\\" class=\\\"CitationRef\\\"\\u003e55\\u003c/span\\u003e\\u003c/sup\\u003e. These coatings, which usually are precipitated on dead tests, are particularly common in methane affected environments, where the precipitation is a result of anaerobic oxidation of methane and sulfate in the SMTZ\\u003csup\\u003e\\u003cspan citationid=\\\"CR44\\\" class=\\\"CitationRef\\\"\\u003e44\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR52\\\" class=\\\"CitationRef\\\"\\u003e52\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR56\\\" class=\\\"CitationRef\\\"\\u003e56\\u003c/span\\u003e\\u003c/sup\\u003e. The process releases bicarbonate and hydrogen sulfide.\\u003c/p\\u003e \\u003cp\\u003eThe δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC measurements in this study are based on well-preserved pristine-looking tests. It is nevertheless conceivable that some tests could have had invisible coatings on their inside affecting the original δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values of the living foraminifera. Given the low δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC we obtained in the calcareous nodules (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ec\\u0026ndash;e), it is possible that even a thin coating could affect some of the measured foraminiferal values. The δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values are elevated in the nodules compared to the benthic foraminiferal values but we note that our measured δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values are similar to and not higher than the values from the non-seep core 1252 (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ed, Fig. S3a,d) and other Nordic Seas non-seep records\\u003csup\\u003e\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e\\u003c/sup\\u003e. We point out that if the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values of the foraminifera were dominated by values from authigenic carbonates precipitated at a migrating SMTZ level, we would expect a random distribution of the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values and not the clear correlation to the DO climatic events we see (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ee).\\u003c/p\\u003e \\u003cp\\u003eThe validity of the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC curve of core 940 as reflecting changes in the emission of methane is supported by several other studies from the Nordic Seas. In core PS62/015\\u0026thinsp;\\u0026minus;\\u0026thinsp;3 from a methane seep at 980 m water depth in Denmark Strait, Millo et al.\\u003csup\\u003e\\u003cspan citationid=\\\"CR34\\\" class=\\\"CitationRef\\\"\\u003e34\\u003c/span\\u003e\\u003c/sup\\u003e observed a similar stratigraphic distribution of low δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ea). In a section referred to MIS 3, the researchers found low δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC in the major interstadials of IS17 to IS8 in a pattern similar to ours and in the long-lasting Heinrich stadials and stadials of MIS 5 and MIS 3, the methane was released before the end of the events similar to H5, S12 and H1 in core 940, while in shorter lasting events the increase was limited to the subsequent interstadial phases\\u003csup\\u003e\\u003cspan citationid=\\\"CR34\\\" class=\\\"CitationRef\\\"\\u003e34\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e). Moreover, a comparable distribution of δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values occurs in Heinrich stadials H4, H3 and H2 in core HH12-930GC from the active pockmark field at 1200 m water depth on the eastern part of Vestnesa Ridge\\u003csup\\u003e\\u003cspan citationid=\\\"CR57\\\" class=\\\"CitationRef\\\"\\u003e57\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003eb).\\u003c/p\\u003e \\u003cp\\u003eIt is also important to notice that core 940 is characterized by many carbonate nodules which occur exclusively in the interstadials indicating that methane oxidizing and sulfate reducing microbes were active\\u003csup\\u003e\\u003cspan citationid=\\\"CR44\\\" class=\\\"CitationRef\\\"\\u003e44\\u003c/span\\u003e\\u003c/sup\\u003e (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e, \\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e). The very low δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values signal a strong discharge of methane\\u003csup\\u003e\\u003cspan citationid=\\\"CR58\\\" class=\\\"CitationRef\\\"\\u003e58\\u003c/span\\u003e\\u003c/sup\\u003e and the increased δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values of the nodules indicate gas hydrate dissociation\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR60\\\" citationid=\\\"CR59\\\" class=\\\"CitationRef\\\"\\u003e59\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR61\\\" class=\\\"CitationRef\\\"\\u003e61\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ed,e). New research indicates that such nodules in periods with strong seepage tend to form near or at the sediment surface, although they at low seepage also can form deeper in the sediment but at a low rate\\u003csup\\u003e\\u003cspan citationid=\\\"CR56\\\" class=\\\"CitationRef\\\"\\u003e56\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR59\\\" class=\\\"CitationRef\\\"\\u003e59\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR62\\\" class=\\\"CitationRef\\\"\\u003e62\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR63\\\" class=\\\"CitationRef\\\"\\u003e63\\u003c/span\\u003e\\u003c/sup\\u003e. A case study of multicore MUC12 from the eastern active pockmarks at Vestnesa Ridge in a location of strong seepage and presence of bacterial mats, the SMTZ was located 0\\u0026ndash;1 cm below the seabed\\u003csup\\u003e\\u003cspan citationid=\\\"CR50\\\" class=\\\"CitationRef\\\"\\u003e50\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003eb). Total alkalinity was at maximum at 0 cm. The rates of sulfate reduction were at maximum at 0\\u0026ndash;3 cm below the seabed and methane oxidation rate was at maximum at 3 cm depth.\\u003c/p\\u003e \\u003cp\\u003eAdditional evidence on changes in the environmental conditions during the investigated period are found in the chemosymbiotic bivalves. They rely on hydrogen sulfide for metabolism. They occur mainly in areas of low to moderate seepage and are absent in areas with intense seepage and toxic levels of sulfide\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR64\\\" citationid=\\\"CR63\\\" class=\\\"CitationRef\\\"\\u003e63\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR65\\\" class=\\\"CitationRef\\\"\\u003e65\\u003c/span\\u003e\\u003c/sup\\u003e. In core 940, they are recorded only in layers correlating with the major stadials and Heinrich stadials of δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC above \\u0026minus;\\u0026thinsp;3\\u0026permil; and being absent in the interstadials (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ec). This is in good agreement with the interpretations presented above of modest seepage during stadials and Heinrich stadials and strong seepage during interstadials.\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eTiming, and magnitude of increased seepage.\\u003c/b\\u003e In this investigation we have shown that during the period 50\\u0026ndash;12 ka, the highest emissions of methane occurred when the bottom water was coldest (\\u0026lt;\\u0026thinsp;0\\u0026ndash;2\\u0026deg;C), while the lowest occurred when the bottom water was warmest (3\\u0026ndash;\\u0026gt;5\\u0026deg;C). This is opposite to nearly all modern observations from shallow sites which find that there is an immediate positive correlation between water temperature and the dissociation of gas from gas hydrates\\u003csup\\u003e\\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e23\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR30\\\" class=\\\"CitationRef\\\"\\u003e30\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR32\\\" class=\\\"CitationRef\\\"\\u003e32\\u003c/span\\u003e,\\u003cspan additionalcitationids=\\\"CR67 CR68\\\" citationid=\\\"CR66\\\" class=\\\"CitationRef\\\"\\u003e66\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR69\\\" class=\\\"CitationRef\\\"\\u003e69\\u003c/span\\u003e\\u003c/sup\\u003e. However, it agrees with model experiments from deep sites which indicate that up to several thousands of years can pass from warming to increased gas release\\u003csup\\u003e\\u003cspan citationid=\\\"CR68\\\" class=\\\"CitationRef\\\"\\u003e68\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR69\\\" class=\\\"CitationRef\\\"\\u003e69\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003eThe stadials in the Nordic Seas are distinguished by increasing bottom water temperatures, surface water stratification and dense cover of sea ice\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR12\\\" citationid=\\\"CR11\\\" class=\\\"CitationRef\\\"\\u003e11\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003e. However, the seepage of gas remained low to moderate until the very end of the stadials signifying that the higher temperatures first at that point in time reached the deep, high concentrations of gas hydrates. In terms of years, the delayed reaction relative to the first rise in water temperatures is in the order of 500 to \\u0026gt;\\u0026thinsp;1000 years. The warm bottom water is at the beginning of the interstadials rapidly replaced by cold bottom water\\u003csup\\u003e\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan additionalcitationids=\\\"CR8\\\" citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ea,f). The response in gas emission to the cooling is delayed with a time factor that resembles the delayed response to the warmings at the beginning of the stadials (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003eb,e).\\u003c/p\\u003e \\u003cp\\u003eThe deposits of the B\\u0026oslash;lling-Aller\\u0026oslash;d interstadials are disturbed from 520\\u0026ndash;260 cm with obliterated sediment structures, abundant pyrite, and a dominance of poorly preserved and apparently reworked foraminifera (Fig. S2c, see Methods). The reworked faunas include many large, abraded specimens of \\u003cem\\u003eC. wuellerstorfi\\u003c/em\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ef). The most likely cause for these disturbances is turbulence instigated by an intense emission of methane. Upward gas migration is also indicated by the vertical channels in the sediment and by the chaotic isotope values and a fauna distribution pattern with many horizons totally without foraminifera (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e, Figs. S1, S2). A possible analogue situation could be a human-induced blowout crater from a gas pipe outburst in the North Sea, where small, dead foraminiferal shells were brought in suspension and removed from the area resulting in a local enrichment of large forms\\u003csup\\u003e\\u003cspan citationid=\\\"CR53\\\" class=\\\"CitationRef\\\"\\u003e53\\u003c/span\\u003e\\u003c/sup\\u003e. An extraordinary strong seepage during the B\\u0026oslash;lling-Aller\\u0026oslash;d interstadials is not surprising considering that the preceding Heinrich stadial H1 experienced the highest bottom water temperatures recorded in the history of core 940 (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003eb, \\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003ea,b). Widespread occurrences of low δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC values during the B\\u0026oslash;lling-Aller\\u0026oslash;d interstadials indicate that similar emissions occurred simultaneously over large areas of the western Svalbard margin\\u003csup\\u003e\\u003cspan citationid=\\\"CR40\\\" class=\\\"CitationRef\\\"\\u003e40\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR55\\\" class=\\\"CitationRef\\\"\\u003e55\\u003c/span\\u003e\\u003c/sup\\u003e including shelf areas\\u003csup\\u003e\\u003cspan citationid=\\\"CR29\\\" class=\\\"CitationRef\\\"\\u003e29\\u003c/span\\u003e\\u003c/sup\\u003e. Another contributory cause to the widespread and strong emission of methane during the B\\u0026oslash;lling and Aller\\u0026oslash;d interstadials could be tectonic movements due to the proximity of the Knipovich Ridge spreading zone\\u003csup\\u003e\\u003cspan citationid=\\\"CR37\\\" class=\\\"CitationRef\\\"\\u003e37\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR45\\\" class=\\\"CitationRef\\\"\\u003e45\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR70\\\" class=\\\"CitationRef\\\"\\u003e70\\u003c/span\\u003e\\u003c/sup\\u003e, isostatic rebound\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR72\\\" citationid=\\\"CR71\\\" class=\\\"CitationRef\\\"\\u003e71\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR73\\\" class=\\\"CitationRef\\\"\\u003e73\\u003c/span\\u003e\\u003c/sup\\u003e and/or high sedimentation rates\\u003csup\\u003e\\u003cspan citationid=\\\"CR35\\\" class=\\\"CitationRef\\\"\\u003e35\\u003c/span\\u003e\\u003c/sup\\u003e. However, the fact that the changes in gas seepage occurs on a millennial time scale, suggests that the primary trigger most likely was the high BWT. Tectonism/isostatic rebound have slower response times and may have prolonged the periods of seepage. During MIS 3 the surrounding ice sheets were small and mainly located inland\\u003csup\\u003e\\u003cspan citationid=\\\"CR74\\\" class=\\\"CitationRef\\\"\\u003e74\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR75\\\" class=\\\"CitationRef\\\"\\u003e75\\u003c/span\\u003e\\u003c/sup\\u003e and the millennial-scale events were probably too short to induce substantial effects from tectonism/isostatic rebounds. Furthermore, sea level changes were small during DO events\\u003csup\\u003e\\u003cspan citationid=\\\"CR76\\\" class=\\\"CitationRef\\\"\\u003e76\\u003c/span\\u003e\\u003c/sup\\u003e and the effect of changes in hydrostatic pressure is small at this water depth\\u003csup\\u003e\\u003cspan citationid=\\\"CR77\\\" class=\\\"CitationRef\\\"\\u003e77\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003eCompared to modern observations of a positive relationship between bottom water temperatures and the dissociation of methane from gas hydrates, the nearly inverse relationship disclosed in core 940 is surprising. Nevertheless, the inverse correlation is repeated 12 times, one for each DO event, and we consider the finding to be reliable, also because a similar pattern was found at other seep sites\\u003csup\\u003e\\u003cspan citationid=\\\"CR34\\\" class=\\\"CitationRef\\\"\\u003e34\\u003c/span\\u003e\\u003c/sup\\u003e. The results of core 940 indicate that the inverse relationship is caused by a time lag that most likely is caused by a delay in the transport of heat through the sea bottom sediments. There are no published diffusion rates from Vestnesa Ridge, but a heat-flow model by Karstens et al.\\u003csup\\u003e\\u003cspan citationid=\\\"CR35\\\" class=\\\"CitationRef\\\"\\u003e35\\u003c/span\\u003e\\u003c/sup\\u003e for the last deglaciation from the deep-sea Nyegga pockmark area indicated a delay of 1000 years before heat induced by increased sedimentation rates (\\u0026gt;\\u0026thinsp;10 m/ka) reached the gas hydrates and an almost explosive seepage of methane occurred (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ea). In core 940, the time lag between the first warming of the bottom water and the response in methane emission generally varies between 500 and 1000 years although the data suggest that delays of close to 2000 years may have occurred. Our interpretation of the cause for the inverse relationship at site 940 is in good agreement with several studies of present-day methane emission released by warming bottom water. The results of these studies indicate that the slow diffusion of heat and gas through the sediment column can delay the emission of methane with hundreds to thousands of years relative to the initial warming\\u003csup\\u003e\\u003cspan citationid=\\\"CR28\\\" class=\\\"CitationRef\\\"\\u003e28\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR33\\\" class=\\\"CitationRef\\\"\\u003e33\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR35\\\" class=\\\"CitationRef\\\"\\u003e35\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR68\\\" class=\\\"CitationRef\\\"\\u003e68\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR69\\\" class=\\\"CitationRef\\\"\\u003e69\\u003c/span\\u003e\\u003c/sup\\u003e. The temporal estimates in these studies are based on modeling experiments as field data of modern diffusion rates are highly uncertain or completely missing\\u003csup\\u003e\\u003cspan citationid=\\\"CR28\\\" class=\\\"CitationRef\\\"\\u003e28\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR69\\\" class=\\\"CitationRef\\\"\\u003e69\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eImplications\\u003c/b\\u003e. We have studied variations in methane emission at a site from 1294 m water depth northwest of Svalbard for the period\\u0026thinsp;~\\u0026thinsp;50.0\\u0026ndash;6.3 ka. The most significant environmental events are repeated changes in bottom water temperatures and strong release of methane for approximately every 500\\u0026ndash;2000 years. The temperature rises and emission of methane is in almost exact antiphase. We interpret the delay between temperature and methane emission as caused primarily by a slow diffusion of heat through the sediments. The increase in BWT during the twelve DO events at Vestnesa Ridge ranges from 1.2\\u0026ndash;4.7\\u0026deg;C (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e). The average temperature increases from the cold interstadials to the maximum temperature obtained in the stadial/Heinrich stadial is 2\\u0026deg;C/ka (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003ea). The ocean today has taken up 90% of the atmospheric heating from present global warming (see references in ref. 25) and the deep ocean is rapidly warming\\u003csup\\u003e\\u003cspan citationid=\\\"CR25\\\" class=\\\"CitationRef\\\"\\u003e25\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR78\\\" class=\\\"CitationRef\\\"\\u003e78\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR79\\\" class=\\\"CitationRef\\\"\\u003e79\\u003c/span\\u003e\\u003c/sup\\u003e. Deep water at 700\\u0026ndash;2000 m water depth is predicted to warm by 0.2\\u0026deg;C over the next 50 years\\u003csup\\u003e\\u003cspan citationid=\\\"CR79\\\" class=\\\"CitationRef\\\"\\u003e79\\u003c/span\\u003e\\u003c/sup\\u003e which corresponds to 4\\u0026deg;C/ka. This is twice the calculated average rate for the interstadial/stadial (Heinrich stadial) transitions in cores 940 and 1252 (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eAt Vestnesa Ridge, bottom water warmings with temperature rises of ~\\u0026thinsp;3\\u0026ndash;5\\u0026deg;C continued for 500 to \\u0026gt;\\u0026thinsp;1000 years before the emission of methane started to increase and reached a level sufficient for the rapid formation of authigenic carbonate. Transferred to modern conditions at the site, this would suggest that the present warming of the deep oceans could reach similar temperatures and remain warm for several hundreds of years before we would see any significant reaction in the dissociation of the gas from the buried gas hydrates. However, it also implies that the emission would continue for many years after a stop in the discharge of anthropogenic CO\\u003csub\\u003e2\\u003c/sub\\u003e and a subsequent temperature fall.\\u003c/p\\u003e\"},{\"header\":\"Methods\",\"content\":\"\\u003cp\\u003e \\u003cb\\u003eCore handling and logging\\u003c/b\\u003e. Piston core HH12-940PC was taken from a sediment-filled pockmark at 1294 m water depth from the western field of inactive pockmarks on Vestnesa Ridge, northwestern Svalbard margin during a cruise with RV \\u003cem\\u003eHelmer Hanssen\\u003c/em\\u003e in July 2012. The upper part of the 12 m inner core liner imploded at the top and the upper\\u0026thinsp;~\\u0026thinsp;1 m of sediment was severely disturbed and discarded. The lower 838 cm were intact and appeared undisturbed. The sediments consisted mainly of fine-grained hemipelagic mud and glacimarine coarse, or clayey deposits. However, the interval 545 to 260 cm showed several vertical channels or fractures, and the interval 520 to 260 cm had foraminifera barren intervals and reworked, abraded benthic specimens were occasionally observed (Fig. \\u003cspan refid=\\\"MOESM1\\\" class=\\\"InternalRef\\\"\\u003eS1\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eCore HH12-940PC was logged using a GEOTEK Multisensor Core Logger with a mounted loop sensor for magnetic susceptibility before opening at the Department of Geosciences, UiT the Arctic University of Norway, Troms\\u0026oslash;, Norway (Fig. S2a). The core sections were X-rayed on a GEOTEK Standard X-ray CT System (Fig. \\u003cspan refid=\\\"MOESM1\\\" class=\\\"InternalRef\\\"\\u003eS1\\u003c/span\\u003e). After opening the sections were color imaged with a Jai L-107CC 3 CCD RGB line scan camera installed on an Avaatech XRF core scanner (Fig. \\u003cspan refid=\\\"MOESM1\\\" class=\\\"InternalRef\\\"\\u003eS1\\u003c/span\\u003e). The lithological log was obtained based on the GEOTEK logs and X-ray images in combination with sediment visual description and color (Munsell chart) shortly after splitting the sections, the grain size distribution and counts of ice rafted debris (IRD) (see below).\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eSampling and counts of foraminifera and IRD.\\u003c/b\\u003e The entire core was initially sliced in 1-cm samples, weighed, freeze-dried, and weighed again. Samples at 5 cm intervals were taken out and subsequently wet sieved over mesh-sizes 0.063, 0.1, and 0.5 mm. A second round to double the sample resolution to 2.5 cm sample intervals was later done in the lower part\\u0026thinsp;\\u0026gt;\\u0026thinsp;545 cm. In the interval 570\\u0026ndash;555 cm samples at every cm were taken out. All new samples were treated in the same way as the first sample batch.\\u003c/p\\u003e \\u003cp\\u003eAll unsplit sample residues\\u0026thinsp;\\u0026gt;\\u0026thinsp;0.1 mm was spread evenly on a picking tray. Foraminifera were picked from randomly chosen squares until \\u0026gt;\\u0026thinsp;300 specimens of benthic and \\u0026gt;\\u0026thinsp;300 specimens of planktic foraminifera were obtained. The foraminifera were identified to species level (some samples contained too few specimens for quantification). The percentages of benthic and planktic species were calculated separately. The size fraction\\u0026thinsp;\\u0026gt;\\u0026thinsp;0.1 mm was chosen to obtain both small phytodetritus species like \\u003cem\\u003eEpistominella\\u003c/em\\u003e and \\u003cem\\u003eNonionella\\u003c/em\\u003e species and larger important paleoenvironmental indicator species like e.g., \\u003cem\\u003eMelonis barleeanus\\u003c/em\\u003e, and \\u003cem\\u003eCibicidoides wuellerstorfi\\u003c/em\\u003e (see species list in Table \\u003cspan refid=\\\"MOESM1\\\" class=\\\"InternalRef\\\"\\u003eS1\\u003c/span\\u003e). A total of eight planktic species and \\u0026gt;\\u0026thinsp;100 benthic species were identified.\\u003c/p\\u003e \\u003cp\\u003eBenthic foraminiferal species of subpolar to subtropical affinity e.g., \\u003cem\\u003eSigmoilopsis schlumbergeri\\u003c/em\\u003e, \\u003cem\\u003eDiscospirina italica\\u003c/em\\u003e, \\u003cem\\u003eOpththalmidium inconstans\\u003c/em\\u003e, \\u003cem\\u003eEggerella bradyi\\u003c/em\\u003e, \\u003cem\\u003eTosaia hanzawaia\\u003c/em\\u003e, \\u003cem\\u003eCibicidoides pachyderma\\u003c/em\\u003e, \\u003cem\\u003eEpistominella decorata\\u003c/em\\u003e, \\u003cem\\u003eGyroidinoides neosoldanii\\u003c/em\\u003e, and \\u003cem\\u003eGyroidina umbonata\\u003c/em\\u003e belonging to an association of subtropical to boreal species and defined as the Atlantic Species Group were added together\\u003csup\\u003e\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR46\\\" class=\\\"CitationRef\\\"\\u003e46\\u003c/span\\u003e\\u003c/sup\\u003e (Table \\u003cspan refid=\\\"MOESM1\\\" class=\\\"InternalRef\\\"\\u003eS1\\u003c/span\\u003e). The concentration of planktic and benthic specimens was calculated as number/g dry weight (dwt) sediment (Fig. S2d,e). Ice rafted debris (IRD) were counted in the \\u0026gt;\\u0026thinsp;0.5 mm size fraction. Number of IRD grains per g dwt sediments was calculated (Fig. S2b). Carbonate-encrustations (nodules) from authigenic precipitation of carbonates from methane seepage and pyrite particles were also counted in the \\u0026gt;\\u0026thinsp;0.5 mm size fraction and concentrations calculated (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ec, Fig. S2c).\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eTransfer functions on the benthic foraminiferal fauna.\\u003c/b\\u003e In core 940 bottom water temperatures (\\u0026deg;C) were estimated by transfer functions using the C2 program\\u003csup\\u003e\\u003cspan citationid=\\\"CR80\\\" class=\\\"CitationRef\\\"\\u003e80\\u003c/span\\u003e\\u003c/sup\\u003e. The calculations were based on the \\u0026gt;\\u0026thinsp;0.1 mm size fraction of benthic foraminifera. We applied the MAT (Modern Analogue Technique) method using 30 analogues. For the calculations we used a database of 401 samples modified from ref. 9 (see references therein). The material consists of previously published records on the distribution of benthic foraminifera in the Nordic Seas and in the northern North Atlantic Ocean. For the calculations we used only samples from the depth interval 250\\u0026ndash;~2000 m.\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eMacrofaunal counts\\u003c/b\\u003e. Presence and quantification of macrofaunas, large foraminifera and pteropods were examined from the \\u0026gt;\\u0026thinsp;0.5 mm size fractions. Chemosymbiotic bivalve species of \\u003cem\\u003eArchivesica arctica\\u003c/em\\u003e, \\u003cem\\u003eIsorropodon nyeggaensis\\u003c/em\\u003e, \\u003cem\\u003eRhagothyas kolgae\\u003c/em\\u003e and \\u003cem\\u003eAcharax svalbardensis\\u003c/em\\u003e (see Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e, Fig. S2) were found in distinct thin layers, while others such as rissoid gastropods, other gastropods, \\u003cem\\u003eYoldiella\\u003c/em\\u003e spp. and \\u003cem\\u003eThyasira\\u003c/em\\u003e spp. were found more scattered in the record. Large bivalves were often broken but hinges were mostly intact and counted as representative of a shell, because eventual paired (but later separated) shells were not easy to match based on hinges alone. Paired shells of \\u003cem\\u003eYoldiella\\u003c/em\\u003e spp. and \\u003cem\\u003eThyasira\\u003c/em\\u003e spp. were common but counted as two to match with other un-paired shell counts.\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eStable isotopes.\\u003c/b\\u003e In core HH12-940PC, stable isotopes δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC and δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO were measured in the polar planktic foraminiferal species \\u003cem\\u003eNeogloboquadrina pachyderma\\u003c/em\\u003e, and benthic species \\u003cem\\u003eCibibidoides wuellerstorfi\\u003c/em\\u003e, \\u003cem\\u003eMelonis barleeanus\\u003c/em\\u003e, and \\u003cem\\u003eCassidulina neoteretis\\u003c/em\\u003e. Only pristine-looking specimens with no visible coating (authigenic precipitation of carbonate, see text for explanation) were picked under a binocular microscope. Several samples in the mid-section 555\\u0026ndash;270 cm contained few benthic and planktic specimens and several foraminiferal specimens were poorly preserved, abraded, fragmented, or coated with authigenic material, therefore in this part benthic isotope analyses were few. Also, deeper in the core some samples were devoid of pristine benthic specimens leaving gaps in the records (marked by black vertical bars in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003ee).\\u003c/p\\u003e \\u003cp\\u003eThe specimens from the first sample set collected at 5 cm intervals were analyzed using a Kiel IV-MAT 253 at the Department of Earth Science, University of Bergen, Bergen, Norway. Long-term external precision (1σ error), based on the replication of working standards pooled over a period of weeks to months, is \\u0026le;\\u0026thinsp;0.04\\u0026permil; and \\u0026le;\\u0026thinsp;0.08\\u0026permil; for δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC and δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO, respectively. Results are reported on the VPDB (Vienna Pee Dee Belemnite) scale and referenced to this scale using NBS-19, NBS-18, and internal house standard CM12 (Table S2).\\u003c/p\\u003e \\u003cp\\u003eThe samples from the second sample set were analyzed using a thermoScientific Gasbench II, MAT 253 IRMS at the Department of Geosciences, UiT the Arctic University of Norway, Troms\\u0026oslash;, Norway. The precision of the instrument with 1σ error is \\u0026lt;\\u0026thinsp;0.1 for both δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003eC and δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO on calcite. Three standards were used: Isolab A, Isolab B, and Merck CaCO\\u003csub\\u003e3\\u003c/sub\\u003e (Table S2), each reported on the VPDB scale relative to NBS-18, NBS-19 and LSVEC (Table S2).\\u003c/p\\u003e \\u003cp\\u003eBecause of isotopic disequilibrium, the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values of \\u003cem\\u003eC. wuellerstorfi\\u003c/em\\u003e was corrected by +\\u0026thinsp;0.64\\u0026permil; and \\u003cem\\u003eM. barleeanus\\u003c/em\\u003e by +\\u0026thinsp;0.4\\u0026permil;\\u003csup\\u003e81,82\\u003c/sup\\u003e. The δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values of the benthic species \\u003cem\\u003eC. neoteretis\\u003c/em\\u003e and the planktic species \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e were not corrected.\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eCalculations of bottom water temperature increases and rate of increases\\u003c/b\\u003e. For both cores the calculation of temperature increases were based on the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values by taking the difference between the maximum δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO values at the end of an interstadial and the minimum values obtained in the subsequent stadial/Heinrich stadial. The calculated differences were corrected for the ice volume change using the sea level curve of ref. 76. For core HH15-1252PC we also calculated the temperature differences between the interstadials and stadial/Heinrich stadials using the minimum Mg/Ca temperature and maximum Mg/Ca temperature for each DO event. We refrained from using the temperatures calculated by transfer functions in core HH12-940PC. In the Svalbard region, the calculations based on benthic species seem to slightly overestimate the lowest temperatures between \\u0026minus;\\u0026thinsp;1 and 1\\u0026deg;C\\u003csup\\u003e\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e\\u003c/sup\\u003e. The rates of temperature increases were calculated for each event by dividing the calculated ranges of temperature rises by the time of minimum temperature to the maximum based on the NGRIP ice core age model\\u003csup\\u003e\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eAMS-\\u003c/b\\u003e \\u003csup\\u003e \\u003cb\\u003e \\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e \\u003c/b\\u003e \\u003c/sup\\u003e \\u003cb\\u003eC dates.\\u003c/b\\u003e In core HH12-940PC, samples of monospecific \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e, chemosymbiotic bivalves, and small non-chemosymbiotic bivalves were dated (Table\\u0026nbsp;1). In two cases, the levels dated by \\u003cem\\u003eN. pachyderma\\u003c/em\\u003e were also dated using chemosymbiotic bivalves. Mixed planktic and benthic foraminiferal faunas were dated in intervals where dateable material was scarce, sometimes supplemented by small specimens of non-chemosymbiotic bivalves (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ee; Table\\u0026nbsp;1). We allow these datings based on mixed benthic and planktic material, because there is only a small difference in reservoir effect between surface and bottom in the Nordic Seas\\u003csup\\u003e\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR17\\\" class=\\\"CitationRef\\\"\\u003e17\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003eThe AMS \\u003csup\\u003e\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e\\u003c/sup\\u003eC dates were performed at the 14Chrono Centre, Queen\\u0026rsquo;s University, Belfast, Northern Ireland, UK. To calibrate the radiocarbon ages, we used the approach presented in Heaton et al.\\u003csup\\u003e\\u003cspan citationid=\\\"CR83\\\" class=\\\"CitationRef\\\"\\u003e83\\u003c/span\\u003e\\u003c/sup\\u003e which accounts for some latitudinal and regional uncertainties related to \\u003csup\\u003e\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e\\u003c/sup\\u003eC depletion during glacial periods.\\u003c/p\\u003e \\u003cp\\u003eWe extracted the average regional marine radiocarbon reservoir age (ΔR) from the \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003ehttp://calib.org/marine/\\u003c/span\\u003e\\u003cspan address=\\\"http://calib.org/marine/\\\" targettype=\\\"URL\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e database based on the seven nearest modern-day ΔR. This resulted in a ΔR=-65\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;33 \\u003csup\\u003e14\\u003c/sup\\u003eC years for our study area (Table\\u0026nbsp;1). Individual samples were then calibrated using the IntCal 0.3.1 package (\\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003ehttps://cran.rproject.org/web/packages/IntCal/IntCal.pdf\\u003c/span\\u003e\\u003cspan address=\\\"https://cran.rproject.org/web/packages/IntCal/IntCal.pdf\\\" targettype=\\\"URL\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eWe used Bayesian age-depth modelling (Table\\u0026nbsp;1), the Marine20 calibration curve\\u003csup\\u003e\\u003cspan citationid=\\\"CR83\\\" class=\\\"CitationRef\\\"\\u003e83\\u003c/span\\u003e\\u003c/sup\\u003e and the rBacon 3.1.1 package\\u003csup\\u003e\\u003cspan citationid=\\\"CR84\\\" class=\\\"CitationRef\\\"\\u003e84\\u003c/span\\u003e\\u003c/sup\\u003e in R software for the age-depth plot (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea). The ages in this paper is presented using the modern ΔR. The mid-points of obtained age ranges were chosen, and calibrated ages are reported with 1σ error (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea; Table\\u0026nbsp;1).\\u003c/p\\u003e \\u003cp\\u003eTo test our identification of individual DO events and their subdivision into stadials/Heinrich stadials and interstadials, we correlated the events in core 940 to the same events as they are defined in the δ\\u003csup\\u003e\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e\\u003c/sup\\u003eO record of the NGRIP ice core (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb) and to the events in nearby marine core 1252\\u003csup\\u003e12\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e, Figs. S3, S4). While the identification of the individual DO events in the two marine cores appear straightforward, it is evident that there is a divergence between the calibrated ages of the events in the marine cores and their ages in the NGRIP time scale. This time difference amounts of ~\\u0026thinsp;1000 years in MIS 2 and parts of MIS 3 undoubtedly reflecting an increase in the reservoir age during the glacial (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb). We refrain from plotting our data on an age scale as the profound changes in sedimentation rates stretches some intervals while compressing others making figures difficult to overview (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb,c).\\u003c/p\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003cp\\u003e \\u003ch2\\u003eCompeting interests:\\u003c/h2\\u003e \\u003cp\\u003eThe authors declare no competing interests.\\u003c/p\\u003e \\u003c/p\\u003e\\u003ch2\\u003eAuthor Contribution\\u003c/h2\\u003e\\u003cp\\u003eThe study was developed by TLR and ET. TLR, NEA, and ET provided the data. The original draft was written by TLR, and all authors participated in writing and editing\\u003c/p\\u003e\\u003ch2\\u003eAcknowledgement\\u003c/h2\\u003e\\u003cp\\u003eWe thank the captain and crew of RV Helmer Hansen and participants of cruise GEO-8144/3144 in 2012 for their assistance in core retrieval and handling. The cruise was funded by the Research School in Arctic Marine Geology and Geophysics (AMGG, the Arctic University of Norway, Troms\\u0026oslash;). The study was funded by the Research Council of Norway through its Centers of Excellence funding scheme, grant number 223259. Ulysses Ninnemann supervised the stable isotope measurements in Bergen and Matteus Lindgren the measurements in Troms\\u0026oslash;\\u003c/p\\u003e\\u003ch2\\u003eData Availability\\u003c/h2\\u003e\\u003cp\\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request. The data will be made available at the UiT Open Research Data repository upon acceptance and publication of this manuscript.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\u003cli\\u003e\\u003cspan\\u003eBond, G. \\u003cem\\u003eet al\\u003c/em\\u003e. Correlations between climate records from North Atlantic and Greenland ice. 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Bayesian Anal. 6, 457\\u0026ndash;474. doi:\\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003e10.1214/11-BA618\\u003c/span\\u003e\\u003cspan address=\\\"10.1214/11-BA618\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e (2011).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eLocarnini, R. A. \\u003cem\\u003eet al\\u003c/em\\u003e. World Ocean Atlas 2018. In A. Mishonov Technical (Ed.), \\u003cem\\u003eNOAA Atlas NESDIS 81\\u003c/em\\u003e (Volume 1: Temperature, p. 52) (2018).\\u003c/span\\u003e\\u003c/li\\u003e\\u003c/ol\\u003e\"},{\"header\":\"Tables\",\"content\":\"\\u003cp\\u003eTable 1 is available in the Supplementary Files section.\\u003c/p\\u003e\"}],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":true,\"hasOptedInToPreprint\":true,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":false,\"hideJournal\":false,\"highlight\":\"\",\"institution\":\"\",\"isAcceptedByJournal\":true,\"isAuthorSuppliedPdf\":false,\"isDeskRejected\":\"\",\"isHiddenFromSearch\":false,\"isInQc\":false,\"isInWorkflow\":false,\"isPdf\":false,\"isPdfUpToDate\":true,\"isWithdrawnOrRetracted\":false,\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"scientific-reports\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"scirep\",\"sideBox\":\"Learn more about [Scientific Reports](http://www.nature.com/srep/)\",\"snPcode\":\"\",\"submissionUrl\":\"\",\"title\":\"Scientific Reports\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"stoa\",\"reportingPortfolio\":\"Scientific Reports\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":true},\"keywords\":\"\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-4149143/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-4149143/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eDuring the last glaciation, the northern hemisphere experienced profound millennial-scale changes (termed Dansgaard-Oeschger (DO) events) in atmospheric and oceanic temperatures. In the North Atlantic, the fluctuations resulted in extremely unstable bottom water conditions with bottom water temperatures (BWT) varying up to \\u0026gt;\\u0026thinsp;5\\u0026deg;C. We have studied these environmental changes in a core from 1300 m water depth at Vestnesa Ridge, northwestern Svalbard margin to investigate a possible connection between BWT and seepage of methane from the seafloor covering the period\\u0026thinsp;~\\u0026thinsp;50\\u0026ndash;6 ka. Beneath Vestnesa Ridge, gas hydrates containing vast amounts of methane are kept stable due to the high pressure and low temperatures. Release of gas is shown by numerous pockmarks on the seafloor. The pockmarks at 1300 m water depth are presently inactive, but they bear witness of earlier activity. Our study shows that from ~\\u0026thinsp;50\\u0026ndash;6 ka, the core site experienced repeated increases in BWT and in the emissions of gas, both following the pattern of the DO-events. This correspondence in time scale indicates that BWT was the primary forcing factor for the variability in methane release. However, the releases were delayed with up to \\u0026gt;\\u0026thinsp;1000 years compared to initial increase in BWT.\\u003c/p\\u003e\",\"manuscriptTitle\":\"Variations in deep-sea methane seepage linked to millennial-scale changes in bottom water temperatures ~50–6 ka, NW Svalbard margin\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2024-04-05 18:19:39\",\"doi\":\"10.21203/rs.3.rs-4149143/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0},{\"type\":\"decision\",\"content\":\"Revision requested\",\"date\":\"2024-05-21T16:49:41+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2024-05-04T16:06:04+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2024-05-01T14:46:53+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2024-04-13T12:06:30+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"9be8cce5-37d7-47eb-a891-4ee020282705\",\"date\":\"2024-04-09T14:48:14+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"3ada1008-c9e5-4ef3-93eb-0c2e0829225c\",\"date\":\"2024-04-09T09:00:32+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"9f3a675d-0861-4ed3-b113-24c4181275b9\",\"date\":\"2024-04-08T14:20:58+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewersInvited\",\"content\":\"\",\"date\":\"2024-04-07T12:54:46+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorAssigned\",\"content\":\"\",\"date\":\"2024-04-02T12:38:41+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorInvited\",\"content\":\"\",\"date\":\"2024-04-02T12:30:28+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"checksComplete\",\"content\":\"\",\"date\":\"2024-04-02T05:40:23+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"submitted\",\"content\":\"Scientific Reports\",\"date\":\"2024-03-22T10:52:32+00:00\",\"index\":\"\",\"fulltext\":\"\"}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"scientific-reports\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"scirep\",\"sideBox\":\"Learn more about [Scientific Reports](http://www.nature.com/srep/)\",\"snPcode\":\"\",\"submissionUrl\":\"\",\"title\":\"Scientific Reports\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"stoa\",\"reportingPortfolio\":\"Scientific Reports\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":true}}],\"origin\":\"\",\"ownerIdentity\":\"0b5647e8-92cc-4e4b-a5f5-10a92655147e\",\"owner\":[],\"postedDate\":\"April 5th, 2024\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"published-in-journal\",\"subjectAreas\":[{\"id\":30233342,\"name\":\"Earth and environmental sciences/Biogeochemistry\"},{\"id\":30233343,\"name\":\"Earth and environmental sciences/Environmental sciences\"},{\"id\":30233344,\"name\":\"Earth and environmental sciences/Ocean sciences\"}],\"tags\":[],\"updatedAt\":\"2024-09-30T16:01:47+00:00\",\"versionOfRecord\":{\"articleIdentity\":\"rs-4149143\",\"link\":\"https://doi.org/10.1038/s41598-024-72865-3\",\"journal\":{\"identity\":\"scientific-reports\",\"isVorOnly\":false,\"title\":\"Scientific Reports\"},\"publishedOn\":\"2024-09-27 15:57:22\",\"publishedOnDateReadable\":\"September 27th, 2024\"},\"versionCreatedAt\":\"2024-04-05 18:19:39\",\"video\":\"\",\"vorDoi\":\"10.1038/s41598-024-72865-3\",\"vorDoiUrl\":\"https://doi.org/10.1038/s41598-024-72865-3\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-4149143\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-4149143\",\"identity\":\"rs-4149143\",\"version\":[\"v1\"]},\"buildId\":\"qtupq5eGEP_6zYnWcrvyt\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}