Séminaire
The ongoing decline of Arctic sea ice exposes the ocean to anomalous surface heat and freshwater fluxes, resulting in positive buoyancy anomalies that can affect ocean circulation. In this study, we use an optimal flux perturbation framework and comprehensive climate model simulations to estimate the sensitivity of the Atlantic meridional overturning circulation (AMOC) to such buoyancy forcing over the Arctic and globally, and more generally to sea ice decline. We find that on decadal timescales anomalies over the subpolar North Atlantic have the largest impact on the AMOC, while on multi-decadal timescales (longer than 20 years), anomalies in the Arctic become more important. These positive buoyancy anomalies spread from the Arctic to the North Atlantic, weakening the AMOC and its poleward heat transport. Consequently, the Arctic sea ice decline may explain the suggested slow-down of the AMOC and the “Warming Hole” persisting in the subpolar North Atlantic.
eric.guilyardi@locean-ipsl.upmc.fr