Surface Flux Drivers for the Slowdown of the Atlantic Meridional Overturning Circulation in a High‐Resolution Global Coupled Climate Model

• Published in: Journal of Advances in Modeling Earth Systems
• Main Authors: D. A. Putrasahan, K. Lohmann, J.‐S. vonStorch, J. H. Jungclaus, O. Gutjahr, H. Haak
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2019
• Subjects: Atlantic Meridional Overturning Circulation; Wind stress effect; high‐resolution global coupled climate model; flux correction in a coupled system; Physical geography; GB3-5030; Oceanography; GC1-1581; North Atlantic
• Online Access: https://doi.org/10.1029/2018MS001447; https://doaj.org/article/84cb4697dc2d4e0aa9e1b100733b867f

Abstract This paper investigates the causation for the decline of the Atlantic Meridional Overturning Circulation (AMOC) from approximately 17 Sv to about 9 Sv, when the atmospheric resolution of the Max Planck Institute‐Earth System Model is enhanced from ∼1° to ∼0.5°. The results show that the slowdown of the AMOC is caused by the cessation of deep convection. In most modeling studies, this is thought to be controlled by buoyancy fluxes in the convective regions, for example, by surface freshwater flux that is introduced locally or via enormous input from glacier or iceberg melts. While we find that freshwater is still the key to the reduction of AMOC seen in the higher‐resolution run, the freshening of the North Atlantic does not need to be directly caused by local freshwater fluxes. Instead, it can be caused indirectly through winds via a reduced wind‐driven gyre circulation and salinity transport associated to this circulation, as seen in the higher‐resolution run.