Reversibility of North Atlantic Climate Change in Response to Stabilization of Anthropogenic CO2 Emission

In the past 100 years, the subpolar North Atlantic is one of the only regions of the ocean which has cooled; this is likely due to a climate change-induced slowdown of the Atlantic Meridional Overturning Circulation (AMOC). It is less clear how this North Atlantic Warming Hole (NAWH) and the AMOC would respond to a stabilization of greenhouse gas emissions. We analyzed six climate models in the LongRunMIP dataset, and defined NAWHI as the difference between North Atlantic Warming Hole (NAWH) regional mean SST and global mean SST. All six global climate models in the dataset project an NAWHI decrease in response to CO2 forcing; however, these models disagree on whether the warming hole will recover as CO2 forcing stabilizes. The models fall into two categories: in quick recovery models, NAWHI declines and AMOC strength weakens, but both recover to approximately their initial states, while in extended recovery models, NAWHI and AMOC strength remain at a weaker or depressed state. A high correlation between NAWHI and AMOC strength was found in all models while AMOC weakens, but only in quick recovery models after AMOC stops weakening. This model divergence could be associated with salinity processes.