Recent emergence of Arctic atlantification dominated by climate warming.

Abstract

The Arctic Ocean's Eurasian Basin underwent notable atlantification during the 2010s, characterized by warming of the Atlantic Water layer and increased upper ocean salinity. Despite profound implications for the Arctic climate system and marine ecosystems, the primary drivers of this process remain debated. One hypothesis suggested that alternating phases of the atmospheric Arctic Dipole may have mitigated recent atlantification. Here, we use high-resolution model simulations to disentangle the main contributors to atlantification in the Arctic basin. We show that the decline in Arctic sea ice was the dominant driver, while wind variability associated with the Arctic Dipole played a minor role, contributing slightly rather than mitigating the process. The positive phase of the Arctic Oscillation also made a relatively small contribution. Although recent changes in atmospheric circulation over the Greenland Sea tended to reduce warm water inflow through the Fram Strait, this cooling effect on the Arctic Atlantic Water layer was outweighed by the warming induced by sea ice decline.