Only eddy-resolving models capture the complete range of AMOC responses to surface winds

The Atlantic meridional overturning circulation (AMOC) is the most important carrier of heat in the ocean and a key part of our climate system. Unfortunately, future projections of AMOC remain difficult up to date. One reason is that we do not quite understand the link between AMOC and the westerly winds blowing around Antarctica, which we know will get stronger in a warming climate.

Veit Lüschow and co-authors ran a high-resolution configuration of the global ocean model MPI-OM driven with different wind scenarios at the ocean surface. Compared to the “present day” scenario, the “strong wind” scenario has a slightly stronger upper AMOC branch (in agreement with earlier studies), but it also shows an almost complete decline of the deep AMOC branch. The latter was unforeseen but can be explained with the help of mesoscale ocean eddies that can be explicitly resolved only in high-resolution models; the authors showed that stronger surface winds cause deep eddies to strengthen and decelerate the deep AMOC branch.