Recent state transition of the Arctic Ocean’s Beaufort Gyre

The anti-cyclonic Beaufort Gyre is the dominant circulation of the Canada Basin and the largest freshwater reservoir in the Arctic Ocean. During the first part of the 2000s, the gyre intensified, expanded and accumulated freshwater. Using an extensive hydrographic dataset from 2003 to 2019, together with updated satellite dynamic ocean topography data, we find that over the past decade the Beaufort Gyre has transitioned to a quasi-stable state in which the increase in sea surface height of the gyre has slowed and the freshwater content has plateaued. In addition, the cold halocline layer, which isolates the warm/salty Atlantic water at depth, has thinned significantly due to less input of cold and salty water stemming from the Pacific Ocean and the Chukchi Sea shelf, together with greater entrainment of lighter water from the eastern Beaufort Sea. This recent transition of the Beaufort Gyre is associated with a southeastward shift in its location as a result of variation in the regional wind forcing. Our results imply that continued thinning of the cold halocline layer could modulate the present stable state, allowing for a freshwater release. This, in turn, could freshen the subpolar North Atlantic, impacting the Atlantic Meridional Overturning Circulation. The Arctic Ocean’s Beaufort Gyre has transitioned to a state where the freshwater content has plateaued and the cold halocline layer has thinned, as a result of variation in the regional wind forcing.