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Transient overturning compensation between Atlantic and Indo-Pacific basins

Sun, Shantong and Thompson, Andrew F. (2020) Transient overturning compensation between Atlantic and Indo-Pacific basins. Journal of Physical Oceanography, 50 (8). pp. 2151-2172. ISSN 0022-3670.

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Climate models consistently project (i) a decline in the formation of North Atlantic Deep Water (NADW) and (ii) a strengthening of the Southern Hemisphere westerly winds in response to anthropogenic greenhouse gas forcing. These two processes suggest potentially conflicting tendencies of the Atlantic meridional overturning circulation (AMOC): a weakening AMOC due to changes in the North Atlantic but a strengthening AMOC due to changes in the Southern Ocean. Here we focus on the transient evolution of the global ocean overturning circulation in response to a perturbation to the NADW formation rate. We propose that the adjustment of the Indo-Pacific overturning circulation is a critical component in mediating AMOC changes. Using a hierarchy of ocean and climate models, we show that the Indo-Pacific overturning circulation provides the first response to AMOC changes through wave processes, whereas the Southern Ocean overturning circulation responds on longer (centennial to millennial) time scales that are determined by eddy diffusion processes. Changes in the Indo-Pacific overturning circulation compensate AMOC changes, which allows the Southern Ocean overturning circulation to evolve independently of the AMOC, at least over time scales up to many decades. In a warming climate, the Indo-Pacific develops an overturning circulation anomaly associated with the weakening AMOC that is characterized by a northward transport close to the surface and a southward transport in the deep ocean, which could effectively redistribute heat between the basins. Our results highlight the importance of interbasin exchange in the response of the global ocean overturning circulation to a changing climate.

Item Type:Article
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URLURL TypeDescription Simulations ItemSource Code ItemSource Code
Sun, Shantong0000-0002-6932-5589
Thompson, Andrew F.0000-0003-0322-4811
Additional Information:© 2020 American Meteorological Society. Manuscript received 18 March 2020, in final form 2 June 2020. Without implying their endorsement, we thank Andrew Stewart, Geoffrey Vallis, and Shang-Ping Xie for helpful discussions. We are also grateful for Dan Jones and an anonymous reviewer for their helpful comments. This work was supported by National Science Foundation (NSF) Grants OPP-1644172 and OPP-1643445. The model simulations in this study were carried out on Cheyenne (doi:10.5065/D6RX99HX), which is provided by NCAR’s Computational and Information System Laboratory, sponsored by the National Science Foundation. The source code for the reduced gravity model is available online ( The code for calculating the isopycnal overturning circulation streamfunction from the nominal 1°-resolution CESM output is also available (
Funding AgencyGrant Number
Subject Keywords:Ocean circulation, Ocean dynamics
Issue or Number:8
Record Number:CaltechAUTHORS:20200716-101103298
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Official Citation:Sun, S., A. F. Thompson, and I. Eisenman, 2020: Transient Overturning Compensation between Atlantic and Indo-Pacific Basins. J. Phys. Oceanogr., 50, 2151–2172,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104402
Deposited By: Tony Diaz
Deposited On:16 Jul 2020 21:18
Last Modified:29 Oct 2020 19:22

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