Rapid 21st century warming in the Southern Indian Ocean driven by altered inter-basin connections

Rapid 21st century warming in the Southern Indian Ocean driven by altered inter-basin connections | 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 Rapid 21st century warming in the Southern Indian Ocean driven by altered inter-basin connections Abhisek Chatterjee, Sajidh C K, Raghu Murtugudde, Michael McPhaden, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4247247/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The Indian Ocean has been warming rapidly over the last few decades. However, this warming has not been uniform; with the subtropical and tropical Southern Indian Ocean (SIO, 5°S3-5°S) cooling until the late 20th Century and then warming abruptly after 2000. Increased Indonesian throughflow (ITF) into the Indian Ocean during the recent climate hiatus was considered to be the primary reason for this recent warming. Our analysis shows that though the ITF inflow decreased rapidly by ~10% after 2010, the upper ocean SIO continued to gain heat at the rate of 0.56 (±0.02) ×10 22 J/decade. We argue that the increased ITF during the hiatus in global surface warming (1998-2010) initiated the SIO warming, resulting in a weaker Mascarene High and its decoupling from Southern Ocean atmospheric variability. This caused disparity in the poleward shift of the subtropical gyres between the Pacific and the Indian Oceans, resulted in a three-fold increase in the Tasman inflow to the Indian Ocean, offsetting the weakened influence of the ITF. This accumulation of heat further weakened Masacarene High and reduced the Agulhas outflow by ~20% from its peak, causing a positive feedback that continued to warm the upper ocean of SIO. Earth and environmental sciences/Ocean sciences/Physical oceanography Earth and environmental sciences/Climate sciences/Climate change/Climate-change impacts Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Posted 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-4247247","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":297883789,"identity":"53f01173-e9b8-44b4-a26b-2d4f1fd11c5c","order_by":0,"name":"Abhisek Chatterjee","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9klEQVRIie3RPWrDMBTA8eclWVS0PmNIr/BMlm6+ikTBk4eOHkpwFmVxDlA65iISgnQRnQvxYCh4bjcXSqht2kIH52MLRf9JEvohCQH4fJcYMtAAAmC6LPrp9zKdQpg5g8BAUJx4L/64NqbNU+APr6pu85sE+GaLcFeNH1I9C8tcBriTq7h0KAtsUgRqxo95ycgGKgeKpIoC1V0P3ZyA7Ki47oj52HckNANJjhLqiL4qMiAMBhIUvIzrQySuHFm2TRk6qcL+LQonshYHyGxXzt/b+9sZXz012OaLhHOr9dvnOPmJ/Y4m/QeJo+BPXJ+33+fz+f59X+IlUfnwcYQzAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0001-5529-7997","institution":"Indian National Centre for Ocean Information Services, Ministry of Earth Sciences","correspondingAuthor":true,"prefix":"","firstName":"Abhisek","middleName":"","lastName":"Chatterjee","suffix":""},{"id":297883791,"identity":"b7830a99-cb8c-4a3b-83c1-b882237e9ab3","order_by":1,"name":"Sajidh C K","email":"","orcid":"","institution":"Indian National Centre for Ocean Information Services, Ministry of Earth Sciences","correspondingAuthor":false,"prefix":"","firstName":"Sajidh","middleName":"C","lastName":"K","suffix":""},{"id":297883793,"identity":"5d6e088a-602c-4c8b-bee8-1f95c736658a","order_by":2,"name":"Raghu Murtugudde","email":"","orcid":"","institution":"Indian Institute of Technology Bombay","correspondingAuthor":false,"prefix":"","firstName":"Raghu","middleName":"","lastName":"Murtugudde","suffix":""},{"id":297883795,"identity":"dbb771ae-6f6e-4d88-a690-427a44e1cc39","order_by":3,"name":"Michael McPhaden","email":"","orcid":"https://orcid.org/0000-0002-8423-5805","institution":"NOAA/PMEL","correspondingAuthor":false,"prefix":"","firstName":"Michael","middleName":"","lastName":"McPhaden","suffix":""},{"id":297883797,"identity":"4b21d54c-bc55-45c4-a5ea-41d980b13210","order_by":4,"name":"Sathish S C Shenoi","email":"","orcid":"","institution":"Ministry of Earth Sciences","correspondingAuthor":false,"prefix":"","firstName":"Sathish","middleName":"S C","lastName":"Shenoi","suffix":""},{"id":297883798,"identity":"67e4d2fa-2430-49f2-bf8c-094dcca4f11f","order_by":5,"name":"P N Vinayachandran","email":"","orcid":"","institution":"Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science","correspondingAuthor":false,"prefix":"","firstName":"P","middleName":"N","lastName":"Vinayachandran","suffix":""}],"badges":[],"createdAt":"2024-04-10 12:05:36","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4247247/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4247247/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":77146621,"identity":"5503f98d-7015-4ca1-9a83-6bd7c5c3667e","added_by":"auto","created_at":"2025-02-25 14:33:39","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1641051,"visible":true,"origin":"","legend":"","description":"","filename":"sajidhetalCEEv5.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4247247/v1_covered_de8244bd-400e-499f-b597-fd655bda38ed.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Rapid 21st century warming in the Southern Indian Ocean driven by altered inter-basin connections","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4247247/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4247247/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The Indian Ocean has been warming rapidly over the last few decades. However, this warming has not been uniform; with the subtropical and tropical Southern Indian Ocean (SIO, 5°S3-5°S) cooling until the late 20th Century and then warming abruptly after 2000. Increased Indonesian throughflow (ITF) into the Indian Ocean during the recent climate hiatus was considered to be the primary reason for this recent warming. Our analysis shows that though the ITF inflow decreased rapidly by ~10% after 2010, the upper ocean SIO continued to gain heat at the rate of 0.56 (±0.02) ×10\u003csup\u003e22\u003c/sup\u003e J/decade. We argue that the increased ITF during the hiatus in global surface warming (1998-2010) initiated the SIO warming, resulting in a weaker Mascarene High and its decoupling from Southern Ocean atmospheric variability. This caused disparity in the poleward shift of the subtropical gyres between the Pacific and the Indian Oceans, resulted in a three-fold increase in the Tasman inflow to the Indian Ocean, offsetting the weakened influence of the ITF. This accumulation of heat further weakened Masacarene High and reduced the Agulhas outflow by ~20% from its peak, causing a positive feedback that continued to warm the upper ocean of SIO.","manuscriptTitle":"Rapid 21st century warming in the Southern Indian Ocean driven by altered inter-basin connections","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-07 03:54:21","doi":"10.21203/rs.3.rs-4247247/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c16bce6d-836e-4459-a494-5bccc9e07fba","owner":[],"postedDate":"May 7th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":31421286,"name":"Earth and environmental sciences/Ocean sciences/Physical oceanography"},{"id":31421287,"name":"Earth and environmental sciences/Climate sciences/Climate change/Climate-change impacts"}],"tags":[],"updatedAt":"2025-02-25T14:25:30+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-07 03:54:21","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4247247","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4247247","identity":"rs-4247247","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}