Future climate change shaped by inter-model differences in Atlantic meridional overturning circulation response

Katinka Bellomo,Susanna Corti,Michela Angeloni,Jost Von Hardenberg

doi:10.1038/s41467-021-24015-w

Abstract

In climate model simulations of future climate change, the Atlantic Meridional Overturning Circulation (AMOC) is projected to decline. However, the impacts of this decline, relative to other changes, remain to be identified. Here we address this problem by analyzing 30 idealized abrupt-4xCO2 climate model simulations. We find that in models with larger AMOC decline, there is a minimum warming in the North Atlantic, a southward displacement of the Inter-tropical Convergence Zone, and a poleward shift of the mid-latitude jet. The changes in the models with smaller AMOC decline are drastically different: there is a relatively larger warming in the North Atlantic, the precipitation response exhibits a wet-get-wetter, dry-get-drier pattern, and there are smaller displacements of the mid-latitude jet. Our study indicates that the AMOC is a major source of inter-model uncertainty, and continued observational efforts are needed to constrain the AMOC response in future climate change.

Highlights

In climate model simulations of future climate change, the Atlantic Meridional Overturning Circulation (AMOC) is projected to decline
Several studies have examined the impacts of an AMOC shutdown in idealized model experiments where the AMOC is artificially halted[13,14,15], and a few of them have examined the impacts of the AMOC decline in the context of future climate change[17,32,33,34]
We address this question examining how the intermodel range in the AMOC decline affects projected climate change in response to an abrupt quadrupling of CO2 in a suite of 30 climate models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5) and CMIP6 archives

Summary

Introduction

In climate model simulations of future climate change, the Atlantic Meridional Overturning Circulation (AMOC) is projected to decline. Direct observations to monitor the AMOC, which began in 2004 with the RAPID-MOCHA array[3,20], show a decline[21,22,23], internal variability is large and the observed time period is too short to estimate a trend[24,25,26] From these observations it is not yet possible to quantify the anthropogenic contribution to the AMOC decline; model projections of future climate change show a further decline of the AMOC into the 21st century in response to greenhouse gas forcing[27,28]. The consequences of the inter-model spread in the AMOC response, including those on the NAWH, remain uncertain

Methods

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Conclusion