Disentangling AMOC, surface heat flux and dynamic sea level change in the North Atlantic

Abstract:

A rise in global mean sea level is a robust feature of anthropogenic climate change using state-of-the-art atmosphere-ocean general circulation models (AOGCMs). However, there is considerable disagreement over the more policy-relevant regional patterns of sea level rise, especially in the North Atlantic. AOGCM simulations with increasing CO2 forcing indicate a link between the pattern of North Atlantic dynamic sea level (DSL) change and the Atlantic meridional overturning circulation (AMOC) change. We identify a link in the AOGCM spread of the AMOC change per unit surface heat flux change over the subpolar North Atlantic, referred to as the AMOC-SHF scaling, and the North Atlantic DSL and AMOC change.

A conceptual atmosphere-ocean model, capturing the salient ocean dynamics and thermodynamics, is introduced to examine the processes which modulate the AMOC-SHF scaling. Isopycnal mixing, atmosphere-ocean coupling strength and zonal wind stress over the Southern Ocean are found to be positively correlated with the AMOC-SHF scaling in the conceptual model and AOGCM simulations. This result builds our understanding of the interacting atmosphere-ocean feedbacks which will control future North Atlantic DSL change.