Controls on the Strength and Structure of the Atlantic Meridional Overturning Circulation in Climate Models

Abstract State‐of‐the‐art climate models simulate a large spread in the mean‐state Atlantic meridional overturning circulation (AMOC), with strengths varying between 12 and 25 Sv. Here, we introduce a framework for understanding this spread by assessing the balance between the thermal‐wind expressio...

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Bibliographic Details
Published in:Geophysical Research Letters
Main Authors: Manali S. Nayak, David B. Bonan, Emily R. Newsom, Andrew F. Thompson
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2024
Subjects:
ocean overturning circulation
climate models
ocean dynamics
surface processes
Geophysics. Cosmic physics
QC801-809
North Atlantic
Online Access:https://doi.org/10.1029/2024GL109055
https://doaj.org/article/0546740ccaf14b2da0b6ed20d3777707
Description
Summary:Abstract State‐of‐the‐art climate models simulate a large spread in the mean‐state Atlantic meridional overturning circulation (AMOC), with strengths varying between 12 and 25 Sv. Here, we introduce a framework for understanding this spread by assessing the balance between the thermal‐wind expression and surface water mass transformation in the North Atlantic. The intermodel spread in the mean‐state AMOC strength is shown to be related to the overturning scale depth: climate models with a larger scale depth tend to have a stronger AMOC. We present a physically motivated scaling relationship that links intermodel variations in the scale depth to surface buoyancy fluxes and stratification in the North Atlantic, and thus connects North Atlantic surface processes to the interior overturning circulation. Climate models with a larger scale depth tend to have stronger surface buoyancy loss and weaker stratification in the North Atlantic. These results offer a framework for reducing mean‐state AMOC biases in climate models.

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