Impact of the Beaufort Gyre freshwater release on deepwater formation in the North Atlantic

Jiaxu Zhang, University of Washington, CICOES, Seattle, United States, Wilbert Weijer, Los Alamos National Laboratory, Los Alamos, NM, United States, Wei Cheng, Univ of Washington, Seattle, United States, Michael Steele, Univ Washington, Seattle, United States and Tarun Verma, Texas A & M University, College Station, TX, United States
The Beaufort Gyre (BG) is the largest liquid freshwater reservoir of the Arctic Ocean. Observations show a significant increase of its freshwater content over the past 15 years, with the increase reaching 40% of its climatology in 2017. If the freshwater is released into the North Atlantic, the magnitude would excess that of the Great Salinity Anomaly of the 1970s, raising the specter of slowing global ocean circulation. However, whether the BG freshwater can ultimately perturb the North Atlantic deepwater formation is highly uncertain. Here, we assess the impact of a potential BG freshwater release during the historical period, using an eddy-permitting ocean-sea ice model with passive tracers that explicitly track the BG volume and freshwater transport.

Our simulations suggest that more BG-sourced freshwater (36 mSv) reached the North Atlantic during a release phase (1983-1995) of the BG freshwater content than during an accumulation phase (1996-2008), when most BG-sourced water recirculated within the Arctic basin. 70% of this BG-sourced freshwater routed through Davis Strait, while 30% routed through Fram Strait. This BG-sourced freshwater was able to bring down the surface salinity by 0.35 psu in the western Labrador Sea towards the end of the release phase. Although the historical release was not able to induce obvious impact during the phase of harsh winters with very strong convection in the early 1990s, the current BG freshwater content anomaly has almost doubled its historical maximum and a future release may become large enough to dampen the deepwater formation once in conjunction with mild winters.