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A hemispheric asymmetry in poleward ocean heat transport across climates: Implications for overturning and polar warming

Newsom, Emily R. and Thompson, Andrew F. and Adkins, Jess F. and Galbraith, Eric D. (2021) A hemispheric asymmetry in poleward ocean heat transport across climates: Implications for overturning and polar warming. Earth and Planetary Science Letters, 568 . Art. No. 117033. ISSN 0012-821X. doi:10.1016/j.epsl.2021.117033.

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The modern Indo-Pacific oceans absorb more heat from the atmosphere than they release. The resulting energy surplus is exported from the Indo-Pacific by the ocean circulation and lost to the atmosphere from other ocean basins. This heat transport ultimately sustains much of the buoyancy lost to deep water formation at high latitudes, a key component of the global overturning circulation. Despite the fundamental link between inter-basin ocean heat transport and global overturning in today's climate, there is no general understanding of how these phenomena vary with climate state. Here, we use an unprecedented suite of fully-coupled climate model simulations, equilibrated for thousands of years to a wide range of CO₂ levels, to demonstrate that major differences in overturning between climates are related to systematic shifts in ocean heat transport between basins. Uniformly, equilibration to higher CO₂ levels strengthens inter-basin ocean heat transport and global deep water formation. These changes are sustained by increased surface heat uptake within the Indo-Pacific oceans, and increased high-latitude heat loss outside of the Indo-Pacific oceans as the climate warms. However, poleward heat transport and high-latitude heat loss do not increase symmetrically between hemispheres. Between glacial and modern-like states, North Atlantic heat loss intensifies and overturning in the Atlantic strengthens. In contrast, between modern-like and hot climates, heat loss and overturning strengthens in the Southern Ocean. We propose that these differences are linked to a shift in the relative efficiency of northward and southward ocean heat transport — dominated by advection in the North Atlantic and eddy diffusion in the Southern Ocean — with climate state. Our results suggest that, under high CO₂, future ocean heat transport towards Antarctica would increase disproportionately compared to its changes since the last ice age.

Item Type:Article
Related URLs:
URLURL TypeDescription
Newsom, Emily R.0000-0002-3436-3833
Thompson, Andrew F.0000-0003-0322-4811
Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2021 Elsevier B.V. Received 16 November 2020, Revised 7 April 2021, Accepted 27 May 2021, Available online 11 June 2021. This work was funded by the National Oceanic and Atmospheric Administration (NOAA) Climate and Global Change (CGC) Fellowship and the Natural Environment Research Council project NE/P019218/1 (E.R.N), the National Science Foundation (NSF) through grants OCE-1235488 (A.F.T.) and OCE-1559215 (J.F.A), the Packard Foundation (A.F.T.), as well as Compute Canada (No. AYU-503) and the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 682602) (E.D.G.). CRediT authorship contribution statement: Emily Newsom led in designing the study, analyzing the results, and writing the manuscript. Andrew Thompson contributed to the study design, analysis, and manuscript writing. Jess Adkins contributed to the study design, analysis and edited the manuscript Eric Galbraith performed the numerical simulations, interpretation of results, and edited the manuscript. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
National Oceanic and Atmospheric Administration (NOAA)UNSPECIFIED
Natural Environment Research Council (NERC)NE/P019218/1
David and Lucile Packard FoundationUNSPECIFIED
Compute CanadaAYU-503
European Research Council (ERC)682602
Subject Keywords:paleoclimate; climate evolution; ocean overturning circulation; ocean heat transport; climate modeling; Last Glacial Maximum
Record Number:CaltechAUTHORS:20210623-162521767
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Official Citation:Emily R. Newsom, Andrew F. Thompson, Jess F. Adkins, Eric D. Galbraith, A hemispheric asymmetry in poleward ocean heat transport across climates: Implications for overturning and polar warming, Earth and Planetary Science Letters, Volume 568, 2021, 117033, ISSN 0012-821X,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109552
Deposited By: Tony Diaz
Deposited On:23 Jun 2021 18:20
Last Modified:23 Jun 2021 18:20

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