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Enhanced warming of the Arctic region relative to the rest of the globe, known as Arctic amplification, is caused by a variety of diverse factors, many of which are influenced by the Atlantic meridional overturning circulation (AMOC). Here, we quantify the role of AMOC changes in Arctic amplification throughout the twenty-first century by comparing two suites of climate model simulations under the same climate change scenario but with two different AMOC states: one with a weakened AMOC and another with a steady AMOC. We find that a weakened AMOC can reduce annual mean Arctic warming by 2 °C by the end of the century. A primary contributor to this reduction in warming is surface albedo feedback, related to a smaller sea ice loss due to AMOC slowdown. Another major contributor is the changes in ocean heat uptake. The weakened AMOC and its associated anomalous ocean heat transport divergence lead to increased ocean heat uptake and surface cooling. These two factors are inextricably linked on seasonal timescales, and their relative importance for Arctic amplification can vary by season. The weakened AMOC can also abate Arctic warming via lapse rate feedback, creating marked cooling from the surface to lower-to-mid troposphere while resulting in relatively weaker cooling in the upper troposphere. Additionally, the weakened AMOC increases the low-level cloud fraction over the North Atlantic warming hole, causing significant cooling there via shortwave (sw) cloud feedback despite the overall effect of sw cloud feedback being a slight warming of the average temperature over the Arctic. 

Abstract The Arctic sea ice has been rapidly dwindling over the past four decades, significantly impacting the Arctic region and beyond. During the same period, the Atlantic meridional overturning circulation (AMOC) was also found in a declining trend. Here we investigate the role of the AMOC in the recent Arctic sea ice changes by comparing simulations from the Community Climate System Model version 4 with decelerated and stationary AMOCs under anthropogenic climate change. We find that the weakened AMOC can slow down the decline rates of Arctic sea ice area and volume by 36% and 22% between 1980 and 2020, respectively. The decelerated ocean circulation causes a reduction of northward Atlantic heat transport and hence a general interior ocean cooling in the Arctic Mediterranean, which helps alleviate the Arctic sea ice loss primarily through thermodynamic processes occurring at the base of the sea ice.