Uncertainties in the Evolution of South Indian Ocean Subsurface Heat Content in CMIP6 models: The Role of the Indonesian Throughflow and Its Pacific Drivers

Uncertainties in the Evolution of South Indian Ocean Subsurface Heat Content in CMIP6 models: The Role of the Indonesian Throughflow and Its Pacific Drivers | 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 Research Article Uncertainties in the Evolution of South Indian Ocean Subsurface Heat Content in CMIP6 models: The Role of the Indonesian Throughflow and Its Pacific Drivers SAJIDH CK, Salma Jasmine, Abhisek Chatterjee This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9063624/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract The Subtropical Indian Ocean (STIO) has emerged as a prominent warming hotspot since the 1950s under anthropogenic forcing. However, coupled climate models have struggled to reproduce the observed spatial distribution and magnitude of this warming. An analysis using 30 CMIP6 models reveals that the largest inter-model uncertainty in long-term ocean heat uptake over the STIO. In this study, we investigate the causes of this spread, primarily focusing on the role of the Indonesian Throughflow (ITF) and its Pacific linkages. CMIP6 models exhibit large inconsistencies in simulating ITF induced upper ocean (top 700 m) heat content variability in the STIO. A regression-based ITF model (ITF-PAC) using canonical ENSO and ENSO-Modoki indices broadly reproduces a similar relationship between the Pacific climate modes and the STIO heat content, but with a much stronger correlations in models than in reanalysis, suggesting an exaggerated Pacific control in the CMIP6 models. Our results highlight these coupled models possess low skill and large uncertainty in capturing ITF-driven heat content variability and long-term Pacific trends that can modulate STIO warming. Ocean heat content Indonesian throughflow ENSO CMIP6 Internal variability Full Text Supplementary Files SupplementaryMaterial.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 17 Mar, 2026 Reviewers invited by journal 17 Mar, 2026 Editor assigned by journal 16 Mar, 2026 First submitted to journal 08 Mar, 2026 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. 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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-9063624","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":607360423,"identity":"5aa89378-4cf5-4f4b-8882-57494364b038","order_by":0,"name":"SAJIDH CK","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIie2PvQrCMBCADwrpcqFrBjGvUBFE0IcJCE7pG4g4xcWfJ/AdnMQxUuzUB+ioFByEQkFwFFOka1o3wXzD/cB93B2Aw/GbCE0XJqGnTWSdbxQiKgXb7fkoGFZ1s8KX+qqLI3DA9HHPZkMEPz7vbUqYCnHapdBb0PVhJBNzGE6nmVUBIWKqQEBAD31JjMJwYFX49lIreOvLVwsFsnoLXXl5pFooYXYxvyjWU5gMvGjDkDT9wrdyUhZqzAOc5A/5nHcDP07shwEKExgQAMKqntjHK3xdV17ZPO1wOBz/yBtAekS8eN6n2wAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0009-0002-1589-0635","institution":"Indian Institute of Technology Madras","correspondingAuthor":true,"prefix":"","firstName":"SAJIDH","middleName":"","lastName":"CK","suffix":""},{"id":607360424,"identity":"3e9767cc-8765-4850-a919-26ccf5d014e5","order_by":1,"name":"Salma Jasmine","email":"","orcid":"","institution":"ESSO- Indian National Centre for Ocean Information Services","correspondingAuthor":false,"prefix":"","firstName":"Salma","middleName":"","lastName":"Jasmine","suffix":""},{"id":607360425,"identity":"d2d127c8-6f84-4e74-abfc-e5c91e57362e","order_by":2,"name":"Abhisek Chatterjee","email":"","orcid":"","institution":"ESSO- Indian National Centre for Ocean Information Services","correspondingAuthor":false,"prefix":"","firstName":"Abhisek","middleName":"","lastName":"Chatterjee","suffix":""}],"badges":[],"createdAt":"2026-03-08 10:47:39","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9063624/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9063624/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104888541,"identity":"1f0f893c-9d18-4389-9897-077c35ae17a9","added_by":"auto","created_at":"2026-03-18 10:17:03","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2052063,"visible":true,"origin":"","legend":"","description":"","filename":"ManuscriptMainText.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9063624/v1_covered_3d13f398-c426-460c-af68-1c9053048615.pdf"},{"id":104888534,"identity":"be2572d1-b281-4ba1-955e-f4cbf30c3242","added_by":"auto","created_at":"2026-03-18 10:16:57","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":2324943,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-9063624/v1/d0364fa497e3fa4b0b09867b.docx"}],"financialInterests":"","formattedTitle":"Uncertainties in the Evolution of South Indian Ocean Subsurface Heat Content in CMIP6 models: The Role of the Indonesian Throughflow and Its Pacific Drivers","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"climate-dynamics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cldy","sideBox":"Learn more about [Climate Dynamics](https://www.springer.com/journal/382)","snPcode":"382","submissionUrl":"https://submission.nature.com/new-submission/382/3","title":"Climate Dynamics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Ocean heat content, Indonesian throughflow, ENSO, CMIP6, Internal variability","lastPublishedDoi":"10.21203/rs.3.rs-9063624/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9063624/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Subtropical Indian Ocean (STIO) has emerged as a prominent warming hotspot since the 1950s under anthropogenic forcing. 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