Fluctuating Atlantic inflows modulate Arctic atlantification

Enhanced warm, salty subarctic inflows drive high-latitude atlantification, which weakens oceanic stratification, amplifies heat fluxes, and reduces sea ice. In this work, we show that the atmospheric Arctic Dipole (AD) associated with anticyclonic winds over North America and cyclonic winds over Eurasia modulates inflows from the North Atlantic across the Nordic Seas. The alternating AD phases create a “switchgear mechanism.” From 2007 to 2021, this switchgear mechanism weakened northward inflows and enhanced sea-ice export across Fram Strait and increased inflows throughout the Barents Sea. By favoring stronger Arctic Ocean circulation, transferring freshwater into the Amerasian Basin, boosting stratification, and lowering oceanic heat fluxes there after 2007, AD+ contributed to slowing sea-ice loss. A transition to an AD− phase may accelerate the Arctic sea-ice decline, which would further change the Arctic climate system. One of the reasons that Arctic sea ice has been disappearing over the past decades is that warm water from the Atlantic is being advected into the high-latitude ocean in increasing amounts, a process called “atlantification.” But what drives this process? Polyakov et al . show that the large-scale weather pattern called the Arctic Dipole causes atmospheric wind patterns that modulate North Atlantic inflows across the Fram Strait and within the Barents Sea, resulting in variations in Arctic Ocean circulation, freshwater fluxes into the Amerasian Basin, ocean stratification, and heat fluxes (see the Perspective by Bacon). —H. Jesse Smith Shifts in large-scale atmospheric circulation patterns have important consequences for Arctic climate.