Increase in deglacial ocean heat content linked to contrasts in extratropical warming

Chenyu Zhu; Lijing Cheng; Zhengyu Liu; Peter U. Clark

doi:10.1029/2025GL115538

Increase in deglacial ocean heat content linked to contrasts in extratropical warming

Chenyu Zhu, Lijing Cheng, Zhengyu Liu, Peter U. Clark

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Abstract

Proxy-based reconstructions suggest that equilibrium changes in global mean sea surface temperature (ΔGMSST) are nearly equivalent to changes in mean ocean temperature (ΔMOT) on glacial-interglacial timescales over the past 900,000 years. However, the underlying mechanisms responsible for this relationship remain poorly understood. Here we use simulations from Paleoclimate Modeling Intercomparison Project Phase 3 and 4 (PMIP3/4) to investigate equilibrium ΔMOT and its linkage to sea surface temperature changes between the Last Glacial Maximum (LGM, ∼21,000 years ago) and pre-Industrial. Results show that PMIP3/4 simulations generally underestimate proxy-based ΔMOT. Regression analysis reveals that LGM MOT is strongly modulated by mid-latitude SST cooling, with the Southern Ocean having a greater influence compared to other oceanic regions, thus helping explain why models with similar ΔGMSSTs exhibit significantly different ΔMOTs. Additionally, we find a strong relationship between simulated Antarctic sea-ice coverage and Southern Ocean SST changes, with implications for constraining sea-ice reconstructions.

Original language	English
Article number	e2025GL115538
Pages (from-to)	1-10
Number of pages	10
Journal	Geophysical Research Letters
Volume	52
Issue number	14
Early online date	24 Jul 2025
DOIs	https://doi.org/10.1029/2025GL115538
Publication status	Published (in print/issue) - 28 Jul 2025

Bibliographical note

Publisher Copyright:
© 2025 The Author(s).

Data Access Statement

Data to produce the main figures in this paper is available in Zhu (2025).

Funding

This work is jointly supported by the National Natural Science Foundation of China (42106013 to C.Z.) and the National Large Scientific and Technological Infrastructure “Earth System Numerical Simulation Facility” (https://cstr.cn/31134.02.EL).

Funders	Funder number
National Natural Science Foundation of China	42106013

Keywords

deglaciation
extratropical warming
ocean heat content
PMIP3 models

Access to Document

10.1029/2025GL115538

Geophysical Research Letters - 2025 - Zhu - Increase in Deglacial Ocean Heat Content Linked to Contrasts in ExtratropicalFinal published version, 2.67 MBLicence: CC BY-NC

Cite this

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title = "Increase in deglacial ocean heat content linked to contrasts in extratropical warming",

abstract = "Proxy-based reconstructions suggest that equilibrium changes in global mean sea surface temperature (ΔGMSST) are nearly equivalent to changes in mean ocean temperature (ΔMOT) on glacial-interglacial timescales over the past 900,000 years. However, the underlying mechanisms responsible for this relationship remain poorly understood. Here we use simulations from Paleoclimate Modeling Intercomparison Project Phase 3 and 4 (PMIP3/4) to investigate equilibrium ΔMOT and its linkage to sea surface temperature changes between the Last Glacial Maximum (LGM, ∼21,000 years ago) and pre-Industrial. Results show that PMIP3/4 simulations generally underestimate proxy-based ΔMOT. Regression analysis reveals that LGM MOT is strongly modulated by mid-latitude SST cooling, with the Southern Ocean having a greater influence compared to other oceanic regions, thus helping explain why models with similar ΔGMSSTs exhibit significantly different ΔMOTs. Additionally, we find a strong relationship between simulated Antarctic sea-ice coverage and Southern Ocean SST changes, with implications for constraining sea-ice reconstructions.",

keywords = "deglaciation, extratropical warming, ocean heat content, PMIP3 models",

author = "Chenyu Zhu and Lijing Cheng and Zhengyu Liu and Clark, \{Peter U.\}",

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doi = "10.1029/2025GL115538",

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AU - Zhu, Chenyu

AU - Cheng, Lijing

AU - Liu, Zhengyu

AU - Clark, Peter U.

PY - 2025/7/28

Y1 - 2025/7/28

N2 - Proxy-based reconstructions suggest that equilibrium changes in global mean sea surface temperature (ΔGMSST) are nearly equivalent to changes in mean ocean temperature (ΔMOT) on glacial-interglacial timescales over the past 900,000 years. However, the underlying mechanisms responsible for this relationship remain poorly understood. Here we use simulations from Paleoclimate Modeling Intercomparison Project Phase 3 and 4 (PMIP3/4) to investigate equilibrium ΔMOT and its linkage to sea surface temperature changes between the Last Glacial Maximum (LGM, ∼21,000 years ago) and pre-Industrial. Results show that PMIP3/4 simulations generally underestimate proxy-based ΔMOT. Regression analysis reveals that LGM MOT is strongly modulated by mid-latitude SST cooling, with the Southern Ocean having a greater influence compared to other oceanic regions, thus helping explain why models with similar ΔGMSSTs exhibit significantly different ΔMOTs. Additionally, we find a strong relationship between simulated Antarctic sea-ice coverage and Southern Ocean SST changes, with implications for constraining sea-ice reconstructions.

AB - Proxy-based reconstructions suggest that equilibrium changes in global mean sea surface temperature (ΔGMSST) are nearly equivalent to changes in mean ocean temperature (ΔMOT) on glacial-interglacial timescales over the past 900,000 years. However, the underlying mechanisms responsible for this relationship remain poorly understood. Here we use simulations from Paleoclimate Modeling Intercomparison Project Phase 3 and 4 (PMIP3/4) to investigate equilibrium ΔMOT and its linkage to sea surface temperature changes between the Last Glacial Maximum (LGM, ∼21,000 years ago) and pre-Industrial. Results show that PMIP3/4 simulations generally underestimate proxy-based ΔMOT. Regression analysis reveals that LGM MOT is strongly modulated by mid-latitude SST cooling, with the Southern Ocean having a greater influence compared to other oceanic regions, thus helping explain why models with similar ΔGMSSTs exhibit significantly different ΔMOTs. Additionally, we find a strong relationship between simulated Antarctic sea-ice coverage and Southern Ocean SST changes, with implications for constraining sea-ice reconstructions.

KW - deglaciation

KW - extratropical warming

KW - ocean heat content

KW - PMIP3 models

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DO - 10.1029/2025GL115538

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ER -

Increase in deglacial ocean heat content linked to contrasts in extratropical warming

Abstract

Bibliographical note

Data Access Statement

Funding

Keywords

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