Separating Direct Heat Flux Forcing and Freshwater Feedback on AMOC Change Under Global Warming

• Published in: Geophysical Research Letters
• Main Authors: Qin Wen, Chenyu Zhu, Deliang Chen, Mengyu Liu, Liang Ning, Mi Yan, Jian Liu, Zhengyu Liu
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: AMOC; global warming; heat flux; freshwater flux; Geophysics. Cosmic physics; QC801-809; Global warming; North Atlantic; Sea ice; Southern Ocean
• Online Access: https://doi.org/10.1029/2023GL105478; https://doaj.org/article/dd80f9c8209b4222b997c796dabcae3c

Abstract The Atlantic meridional overturning circulation (AMOC) is predicted to weaken under global warming. Whether it is caused by heat flux or freshwater flux is under debate. Here we separate these two processes in changing the AMOC under global warming. The simulated AMOC is weakened during the first 600 years and then gradually recovered to its initial state, with heat flux and freshwater feedback dominating at different timescales. Global warming immediately puts freshwater into the Southern Ocean, which triggers the initial AMOC weakening via altering surface temperature. Concurrently, the extensive heat into the ocean surface increases the temperature over the subpolar North Atlantic, reducing the deep convection and thus the AMOC in the subsequent 50–150 years. Meanwhile, the Arctic sea ice melt leads to the AMOC shutdown. Subsequently, the salinity accumulation in the subtropical North Atlantic propagating northward to restart the North Atlantic deep convection is responsible for the AMOC recovery.