Deus ex machina long-term cooling of the eastern Pacific cold tongue in ocean reanalysis data.
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| Title: | Deus ex machina long-term cooling of the eastern Pacific cold tongue in ocean reanalysis data. |
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| Authors: | Jiang, Feng1 (AUTHOR) fjiang@ldeo.columbia.edu, Seager, Richard1 (AUTHOR), Cane, Mark A.1 (AUTHOR) |
| Source: | Journal of Climate. Jun2026, Vol. 39 Issue 12, p1-16. 16p. |
| Subjects: | Data assimilation, Climate change models, Ocean, Oceanographic observations, Oceanic mixing, Ocean temperature, Heat budget (Geophysics), Oceanography |
| Geographic Terms: | Pacific Ocean |
| Abstract: | The emergence of an observed distinctive, meridionally confined surface cooling trend in the tropical Pacific cold tongue over recent decades contrasts sharply with the rapid warming simulated by most climate models, representing a key unresolved feature of climate change. Ocean-only simulations, even when forced with observed atmospheric conditions, likewise fail to reproduce the observed long-term absence of surface layer warming over the eastern Pacific cold tongue. Here we examine the long-term heat budget of the surface layer in the equatorial Pacific using atmospheric and oceanic reanalysis data, quantifying contributions from surface heat fluxes, ocean advection, and vertical diffusion inferred through Richardson number-based diffusivity estimates. In the Ocean ReAnalysis System 5 (ORAS5), the observed cold tongue cooling cannot be reproduced by the model's intrinsic dynamics alone; instead, it depends on a surface heat flux adjustment imposed during data assimilation. A reduction in the warming effect associated with this adjustment in the eastern Pacific cold tongue over time emerges as the dominant contributor to the long-term cooling in the reanalysis data, a deus ex machina obscuring the actual physical drivers of change in the real ocean. We discuss potential origins of this deus ex machina cooling effect, including the influence of analysis increments, uncertainties in surface forcing and possible problems in the representation of oceanic processes, particularly subsurface turbulent heat flux induced by oceanic mixing processes. This work emphasizes that reanalysis-based assessments remain subject to inherent biases from the ocean models they are built upon. Resolving the discrepancy between observed and simulated Pacific trends will require confronting the structural limitations of models. [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of Climate is the property of American Meteorological Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
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| Header | DbId: egs DbLabel: Engineering Source An: 194578154 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Deus ex machina long-term cooling of the eastern Pacific cold tongue in ocean reanalysis data. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Jiang%2C+Feng%22">Jiang, Feng</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> fjiang@ldeo.columbia.edu</i><br /><searchLink fieldCode="AR" term="%22Seager%2C+Richard%22">Seager, Richard</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Cane%2C+Mark+A%2E%22">Cane, Mark A.</searchLink><relatesTo>1</relatesTo> (AUTHOR) – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Climate%22">Journal of Climate</searchLink>. Jun2026, Vol. 39 Issue 12, p1-16. 16p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Data+assimilation%22">Data assimilation</searchLink><br /><searchLink fieldCode="DE" term="%22Climate+change+models%22">Climate change models</searchLink><br /><searchLink fieldCode="DE" term="%22Ocean%22">Ocean</searchLink><br /><searchLink fieldCode="DE" term="%22Oceanographic+observations%22">Oceanographic observations</searchLink><br /><searchLink fieldCode="DE" term="%22Oceanic+mixing%22">Oceanic mixing</searchLink><br /><searchLink fieldCode="DE" term="%22Ocean+temperature%22">Ocean temperature</searchLink><br /><searchLink fieldCode="DE" term="%22Heat+budget+%28Geophysics%29%22">Heat budget (Geophysics)</searchLink><br /><searchLink fieldCode="DE" term="%22Oceanography%22">Oceanography</searchLink> – Name: SubjectGeographic Label: Geographic Terms Group: Su Data: <searchLink fieldCode="DE" term="%22Pacific+Ocean%22">Pacific Ocean</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: The emergence of an observed distinctive, meridionally confined surface cooling trend in the tropical Pacific cold tongue over recent decades contrasts sharply with the rapid warming simulated by most climate models, representing a key unresolved feature of climate change. Ocean-only simulations, even when forced with observed atmospheric conditions, likewise fail to reproduce the observed long-term absence of surface layer warming over the eastern Pacific cold tongue. Here we examine the long-term heat budget of the surface layer in the equatorial Pacific using atmospheric and oceanic reanalysis data, quantifying contributions from surface heat fluxes, ocean advection, and vertical diffusion inferred through Richardson number-based diffusivity estimates. In the Ocean ReAnalysis System 5 (ORAS5), the observed cold tongue cooling cannot be reproduced by the model's intrinsic dynamics alone; instead, it depends on a surface heat flux adjustment imposed during data assimilation. A reduction in the warming effect associated with this adjustment in the eastern Pacific cold tongue over time emerges as the dominant contributor to the long-term cooling in the reanalysis data, a deus ex machina obscuring the actual physical drivers of change in the real ocean. We discuss potential origins of this deus ex machina cooling effect, including the influence of analysis increments, uncertainties in surface forcing and possible problems in the representation of oceanic processes, particularly subsurface turbulent heat flux induced by oceanic mixing processes. This work emphasizes that reanalysis-based assessments remain subject to inherent biases from the ocean models they are built upon. Resolving the discrepancy between observed and simulated Pacific trends will require confronting the structural limitations of models. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Journal of Climate is the property of American Meteorological Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1175/JCLI-D-25-0356.1 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 16 StartPage: 1 Subjects: – SubjectFull: Data assimilation Type: general – SubjectFull: Climate change models Type: general – SubjectFull: Ocean Type: general – SubjectFull: Oceanographic observations Type: general – SubjectFull: Oceanic mixing Type: general – SubjectFull: Ocean temperature Type: general – SubjectFull: Heat budget (Geophysics) Type: general – SubjectFull: Oceanography Type: general – SubjectFull: Pacific Ocean Type: general Titles: – TitleFull: Deus ex machina long-term cooling of the eastern Pacific cold tongue in ocean reanalysis data. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Jiang, Feng – PersonEntity: Name: NameFull: Seager, Richard – PersonEntity: Name: NameFull: Cane, Mark A. IsPartOfRelationships: – BibEntity: Dates: – D: 15 M: 06 Text: Jun2026 Type: published Y: 2026 Identifiers: – Type: issn-print Value: 08948755 Numbering: – Type: volume Value: 39 – Type: issue Value: 12 Titles: – TitleFull: Journal of Climate Type: main |
| ResultId | 1 |
