Southern Hemisphere Atmosphere Wavenumber 4 driven Marine Heat Waves and Marine Cool Spells

Southern Hemisphere Atmosphere Wavenumber 4 driven Marine Heat Waves and Marine Cool Spells | 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 Southern Hemisphere Atmosphere Wavenumber 4 driven Marine Heat Waves and Marine Cool Spells Stephen Chiswell This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-352621/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 06 Aug, 2021 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract When SST anomalies are defined with respect to a changing baseline and normalised by their 90th percentile, the Tasman Sea is one of the southern hemisphere hotspots of marine heat waves (MHW) and marine cool spells (MCS). There is little evidence that MHW or MCS are increasing in either frequency or intensity, although the duration of MHW has increased from 8 d four decades ago to 26 d now. On average, Tasman Sea MHW/MCS co-occur with MHW/MCS in the Atlantic, Indian, and eastern-Pacific Oceans, in a wavenumber 4 (W4) pattern. Canonical MHW and MCS show they are likely driven by a stalling of the eastward propagation of a W4 atmospheric wave. During MHW, this slow down leads to near-stationary anomalously high and low air pressure areas driving anomalous north-easterly winds over the Tasman Sea. During MCS, similar a slow-down occurs, but shifted by one-half wavelength zonally. Oceanography Marine Heat Waves Marine Cool Spells Global Teleconnections Southern Hemisphere Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Published Journal Publication published 06 Aug, 2021 Read the published version in Nature Communications → Version 1 posted 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-352621","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":19607310,"identity":"3dabd9a0-7197-404c-bcb5-a3abedbc632c","order_by":0,"name":"Stephen Chiswell","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4UlEQVRIie2QsQrCMBCGrxyky2nXuNRXqAi6+SwJgrO7QwNCXHwAwfeoayGDi/gCXSpCH0EcipoWJ8FQN4d8w/Fn+Mh/B+Dx/CcMhJ39EPM2AASqm8KQiR+UdiIl3VoNFVZlWZvYKrfyomcQ7Y3CZf1dSXI2TaQ2Y4a9gw1z4GepcEcOBYhxqQqpsZdxmSEkFCgk7ipmFVEXqUaqrJK+FddeeaOwQthd7HeZeSvCUcywCZf6OdLYhMeR+ClQhnJHsc26GtzrxTAKm3BaxdE2vFzJcTHAj3d7KscfHo/H4+nCC9lgQZYOwEsrAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-5957-3706","institution":"National Institute of Water and Atmospheric Research","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Stephen","middleName":"","lastName":"Chiswell","suffix":""}],"badges":[],"createdAt":"2021-03-22 15:28:46","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-352621/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-352621/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-021-25160-y","type":"published","date":"2021-08-06T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":7666181,"identity":"91f5a39b-9a9a-4bab-aebd-810600c90d5f","added_by":"auto","created_at":"2021-04-05 14:14:41","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1500166,"visible":true,"origin":"","legend":"a) 1982-2020 trend in sea surface temperature, SST, computed from the Reynolds OISST reanalysis; b) 90th percentile in SST anomalies once the trend and annual cycles are removed; c) Number of days between 1982 and 2020 where the SST anomaly exceeded 3 times the 90th percentile. Black lines show the ‘Tasman Box’ used to compute the temperature index, SSTTAS. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-352621/v1/24a37fc38a623d9ee02ffff6.png"},{"id":7666549,"identity":"56a7cdd6-6e3b-46f6-b67f-57266c38bba0","added_by":"auto","created_at":"2021-04-05 14:17:41","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":618239,"visible":true,"origin":"","legend":"Mean SST anomaly, SSTTAS (i.e. with trend and annual cycle removed, and normalised by the 90th percentile) computed over the Tasman Box shown in Figure 1. Circles show peaks of warm and cool ‘events’ when SSTTAS was greater than 1 or less than -1 for at least 5 d. Filled circles indicate the events shown in Figure 3. Also shown is the Southern Oscilation Index (SOI) smoothed with a 6-month window, divided by 2 and plotted with a 6-month lag. ","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-352621/v1/0862887c354234a5897aaad5.png"},{"id":7666548,"identity":"2da18035-10f1-4570-9113-ccd22f74a85d","added_by":"auto","created_at":"2021-04-05 14:17:41","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1863916,"visible":true,"origin":"","legend":"Left-hand panel shows representiative warm events (defined when Tasman Sea mean normalised SST anomaly, SSTTAS, was greater than 1, see Figure 2). Right-hand panels show representative cool events (Tasman Sea mean SSTTAS \u003c-1). The upper panels (23 December 2017 and 1 January 2007) show the strongest warm and cool events, respectively. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-352621/v1/ae65642d822c0c630d2ecc8d.png"},{"id":7666552,"identity":"11a217c6-a811-4b59-9f26-dd6e7f285557","added_by":"auto","created_at":"2021-04-05 14:17:41","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1078183,"visible":true,"origin":"","legend":"a) Mean normalised sea surface temperature anomaly, SSTA, of all 22 warm events (indicated by red circles in Figure 2) and mean air pressure anomaly, PA, for the same events; b) Mean SSTA and PA for all 21 cool events (indicated by blue circles in Figure 2). A to D and X to Z indicate highs and lows discussed in the text. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-352621/v1/234cebb802354c7351a77811.png"},{"id":7666551,"identity":"f0141abe-14cb-4a59-b231-c115bf2f97ce","added_by":"auto","created_at":"2021-04-05 14:17:41","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1418851,"visible":true,"origin":"","legend":"Progression of canonical MHW and MCS (see text). a) Canonical MHW showing sea surface temperature anomaly, SSTA, and air pressure anomaly, PA, from 45 d prior to peak event in Tasman Sea, to 20 d after peak event. A to D indicate highs discussed in the text; b) Corresponding values for canonical MCS. XY and X to Z indicate lows discussed in the text. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-352621/v1/e7df379808e53df4ef9363bc.png"},{"id":7666967,"identity":"e2c8cb8e-fb7f-42ad-a4e2-b2a546acc083","added_by":"auto","created_at":"2021-04-05 14:20:41","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1727903,"visible":true,"origin":"","legend":"Hovmöller diagrams for canonical MHW and MCS at 45°S showing normalised SST anomaly, SSTA, air pressure anomaly, PA, air-sea heat flux anomaly, QA, and wind stress anomaly τA. The peak event occurs at time = 0 d. Labels A to D and X to Z indicate lows shown in Figure 4 and Figure 5. Vertical dashed lines show the longitude of New Zealand at this latitude +/- 90°, +180°. Blank areas in SSTA indicate the land masses of Asutralia, New Zealand, and South America. Sloped solid and longer dashed lines indicate a phase-speed of 5° d-1. Shorter dashed lines indicate slower speeds ascribed to highs (A to D) and lows (W to Z) in PA. The heat convention is that negative values indicate heat entering the ocean. 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There is little evidence that MHW or MCS are increasing in either frequency or intensity, although the duration of MHW has increased from 8 d four decades ago to 26 d now. \r\nOn average, Tasman Sea MHW/MCS co-occur with MHW/MCS in the Atlantic, Indian, and eastern-Pacific Oceans, in a wavenumber 4 (W4) pattern. Canonical MHW and MCS show they are likely driven by a stalling of the eastward propagation of a W4 atmospheric wave. During MHW, this slow down leads to near-stationary anomalously high and low air pressure areas driving anomalous north-easterly winds over the Tasman Sea. During MCS, similar a slow-down occurs, but shifted by one-half wavelength zonally.","manuscriptTitle":"Southern Hemisphere Atmosphere Wavenumber 4 driven Marine Heat Waves and Marine Cool Spells","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-04-05 14:14:39","doi":"10.21203/rs.3.rs-352621/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"471f7297-95c7-461b-888b-42191f072172","owner":[],"postedDate":"April 5th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":3396559,"name":"Oceanography"}],"tags":[],"updatedAt":"2021-11-22T15:35:39+00:00","versionOfRecord":{"articleIdentity":"rs-352621","link":"https://doi.org/10.1038/s41467-021-25160-y","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2021-08-06 04:00:00","publishedOnDateReadable":"August 6th, 2021"},"versionCreatedAt":"2021-04-05 14:14:39","video":"","vorDoi":"10.1038/s41467-021-25160-y","vorDoiUrl":"https://doi.org/10.1038/s41467-021-25160-y","workflowStages":[]},"version":"v1","identity":"rs-352621","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-352621","identity":"rs-352621","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}