{"authors":[{"id":null,"fullName":"Ferster, Brady","name":"Brady","surname":"Ferster","rank":1,"pid":{"id":{"scheme":"orcid_pending","value":"0000-0001-9241-518x"},"provenance":null}}],"openAccessColor":null,"publiclyFunded":false,"eoscIfGuidelines":null,"type":"publication","language":{"code":"eng","label":"English"},"countries":null,"subjects":[{"subject":{"scheme":"keyword","value":"AMOC"},"provenance":null},{"subject":{"scheme":"keyword","value":"North Atlantic Dense Waters"},"provenance":null},{"subject":{"scheme":"keyword","value":"EPOC"},"provenance":null},{"subject":{"scheme":"keyword","value":"abrupt 4xCO2"},"provenance":null},{"subject":{"scheme":"FOS","value":"01 natural sciences"},"provenance":null},{"subject":{"scheme":"keyword","value":"CMIP6"},"provenance":null},{"subject":{"scheme":"FOS","value":"0105 earth and related environmental sciences"},"provenance":null},{"subject":{"scheme":"keyword","value":"Western Subpolar North Atlantic Model Diversity"},"provenance":null}],"mainTitle":"The role of model background mean state in modulating the AMOC response to abrupt CO2 forcing","subTitle":null,"descriptions":["Abstract        The future evolution of the Atlantic Meridional Overturning Circulation (AMOC) under anthropogenic forcing remains uncertain, in part due to limited understanding of how the background ocean state shapes its response. This work investigates the AMOC response to abrupt 4×CO₂ forcing using CMIP6 models, with a focus on the roles of density compensation from temperature (alphaT) and salinity (betaS). Models are classified into thermally-dominated, salinity-dominated, and balanced-compensation regimes based on western subpolar North Atlantic density structure at 500 m depth. Models with background states further from balanced density compensation exhibit the most rapid and persistent AMOC decline, while those with more balanced contributions show slower or more spatially distributed weakening. During the adjustment period (years 11–40), the alphaT to betaS ratio and control AMOC strength together explain ~80 percent of the inter-model variance in AMOC decline.  The spatial structure of mixed layer depth shoaling, sea ice retreat, and surface water mass transformation strongly differs across regimes, with salinity-dominated models showing early loss of deep water formation and strong subpolar stratification. Observational and reanalysis datasets, including WOA18, EN4, and ORAS5, map closest to the thermally-dominated regime within the density compensation framework. This suggests the present-day climate state may be more stable than models with strong salinity control, but still susceptible to future warming and freshening. These results indicate that differences in background climate state and internal variability both shape the timing and magnitude of AMOC weakening, and emphasize that constraining the present-day subpolar ocean state is essential for narrowing uncertainty in future projections.   ******************************************************************************************  Presentation held at the MPI-M & UHH Joint Seminar on 17.06.2025 in Hamburg, Germany. "],"publicationDate":"2025-06-17","publisher":"Zenodo","embargoEndDate":null,"sources":null,"formats":null,"contributors":null,"coverages":null,"bestAccessRight":{"code":"c_abf2","label":"OPEN","scheme":"http://vocabularies.coar-repositories.org/documentation/access_rights/"},"container":null,"documentationUrls":null,"codeRepositoryUrl":null,"programmingLanguage":null,"contactPeople":null,"contactGroups":null,"tools":null,"size":null,"version":null,"geoLocations":null,"id":"doi_dedup___::e4b93eaedd5c67cbd9cd10a7191b4014","originalIds":["50|datacite____::e4b93eaedd5c67cbd9cd10a7191b4014","10.5281/zenodo.15706448","50|datacite____::f0fbc6b861b9ace7014ab865e874f564","10.5281/zenodo.15706449","50|od______2659::f0fbc6b861b9ace7014ab865e874f564","oai:zenodo.org:15706449"],"pids":[{"scheme":"doi","value":"10.5281/zenodo.15706448"},{"scheme":"doi","value":"10.5281/zenodo.15706449"}],"dateOfCollection":null,"lastUpdateTimeStamp":null,"indicators":{"citationImpact":{"citationCount":0.0,"influence":2.2251732E-9,"popularity":2.342466E-9,"impulse":0.0,"citationClass":"C5","influenceClass":"C5","impulseClass":"C5","popularityClass":"C5"}},"projects":[{"id":"corda_____he::23f897659b1a83cb12da0b5919884474","code":"101059547","acronym":"EPOC","title":"Explaining and Predicting the Ocean Conveyor","funder":"European Commission","pids":[{"scheme":"doi","value":"10.3030/101059547"}]}],"organizations":[{"legalName":"Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique","acronym":"CERFACS","id":"openorgs____::e1f5cf89e665d1c10f38bb93ff76a710","pids":[{"scheme":"OrgReg","value":"FR1039"},{"scheme":"GRID","value":"grid.15040.30"},{"scheme":"RNSR","value":"RNSR:201622384R"},{"scheme":"ISNI","value":"0000000406407549"},{"scheme":"PIC","value":"999940118"},{"scheme":"ROR","value":"https://ror.org/02dzbc556"}]}],"communities":[{"code":"eosc","label":"EOSC","provenance":null}],"collectedFrom":[{"key":"openaire____::9e3be59865b2c1c335d32dae2fe7b254","value":"Datacite"},{"key":"opendoar____::358aee4cc897452c00244351e4d91f69","value":"ZENODO"}],"instances":[{"pids":[{"scheme":"doi","value":"10.5281/zenodo.15706448"}],"license":"CC BY","type":"Presentation","urls":["https://dx.doi.org/10.5281/zenodo.15706448"],"publicationDate":"2025-06-17","refereed":"nonPeerReviewed","hostedBy":{"key":"opendoar____::358aee4cc897452c00244351e4d91f69","value":"ZENODO"},"collectedFrom":{"key":"openaire____::9e3be59865b2c1c335d32dae2fe7b254","value":"Datacite"}},{"pids":[{"scheme":"doi","value":"10.5281/zenodo.15706449"}],"license":"CC BY","type":"Presentation","urls":["https://dx.doi.org/10.5281/zenodo.15706449"],"publicationDate":"2025-06-17","refereed":"nonPeerReviewed","hostedBy":{"key":"opendoar____::358aee4cc897452c00244351e4d91f69","value":"ZENODO"},"collectedFrom":{"key":"openaire____::9e3be59865b2c1c335d32dae2fe7b254","value":"Datacite"}},{"pids":[{"scheme":"doi","value":"10.5281/zenodo.15706449"}],"alternateIdentifiers":[{"scheme":"oai","value":"oai:zenodo.org:15706449"}],"license":"CC BY","accessRight":{"code":"c_abf2","label":"OPEN","scheme":"http://vocabularies.coar-repositories.org/documentation/access_rights/","openAccessRoute":null},"type":"Other literature type","urls":["https://zenodo.org/records/15706449","http://dx.doi.org/10.5281/zenodo.15706449"],"publicationDate":"2025-06-17","refereed":"nonPeerReviewed","hostedBy":{"key":"opendoar____::358aee4cc897452c00244351e4d91f69","value":"ZENODO"},"collectedFrom":{"key":"opendoar____::358aee4cc897452c00244351e4d91f69","value":"ZENODO"}}],"links":[{"header":{"relationType":"resultProject","relationClass":"isProducedBy","relatedIdentifier":"corda_____he::23f897659b1a83cb12da0b5919884474","relatedRecordType":"project","relationProvenance":"sysimport:crosswalk:repository","trust":"0.9"},"collectedfrom":[{"dsId":"openaire____::3f264f93cf3b0cfc4ede188a6300455c","dsName":"CORDA - 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