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Abstract:
The relatively warm Summer Pacific Waters (sPW) enter the Arctic via Bering Strait and supply the Canada Basin with heat at 60-100 m depth. The extent to which this subsurface heat reservoir affects the thermodynamic equilibrium of the overlying sea ice remains unknown. While a sharp halocline insulates this heat source from the surface, suggesting a minimal role for the sPW in the sea ice decline, circumstantial evidence suggests a more important role as regions of strong sea ice decline coincide with the location of this heat reservoir. Moreover, recent observations have revealed a significant warming and shoaling of sPW. Here, we characterize the time-mean pathways of sPW and of the winter Pacific Waters (wPW) lying below by computing the Montgomery potential on isopycnal surfaces using the World Ocean Atlas climatologies. The sPW are found to mainly circulate anticyclonically in the upper part of the Beaufort Gyre, as previously documented. The analysis also reveals secondary pathways at the entrance of the Canada Archipelago. Starting in the mid-1990s, an acceleration of the circulation of sPW is observed within the Canada Basin. This acceleration coincides with a reversal of the wPW circulation, from cyclonic to anticyclonic. Changes in PW pathways are attributed to changes in the sea surface height that have been linked to atmospheric circulation pattern and sea ice decline. Finally, the role of mesoscale eddies in transporting heat within the Beaufort Gyre is discussed in light of an estimate of the heat transported by the sPW at seasonal scale.
