The Impact of Winds on AMOC in a Fully-Coupled Climate Model

Here we investigate the role of the atmospheric circulation in the Atlantic Meridional Overturning Circulation (AMOC) by comparing a fully-coupled large ensemble, a forced-ocean simulation, and new experiments using a fully-coupled global climate model where winds above the boundary layer are nudged toward reanalysis. When winds are nudged north of 45 degrees N, agreement with RAPID array observations of AMOC at 26.5 degrees N improves across several metrics. The phasing of interannual variability is well-captured due to the response of the local Ekman component in both wind-nudging and forced-ocean simulations, however the variance remains underestimated. The mean AMOC strength is substantially reduced relative to the fully-coupled model large ensemble, which is biased high, due to the impact of winds on surface buoyancy fluxes over the subpolar gyre. Nudging winds toward observations also reduces the 1979-2016 trend in AMOC, suggesting that improvement in the representation of the high-latitude atmosphere is important for projecting long-term AMOC changes.

Automated summary

This study investigates the role of atmospheric circulation in the Atlantic Meridional Overturning Circulation (AMOC). The results show that adjusting the wind direction has a significant impact on the observed AMOC. However, the current models still underestimate the variance of AMOC and have biases in the mean AMOC strength.