A Review of Arctic-Subarctic Ocean Linkages: Past Changes, Mechanisms, and Future Projections

Arctic Ocean gateway fluxes play a crucial role in linking the Arctic with the global ocean and affecting climate and marine ecosystems.We reviewed past studies on Arctic-Subarctic ocean linkages and examined their changes and driving mechanisms.Our review highlights that radical changes occurred in the inflows and outflows of the Arctic Ocean during the 2010s.Specifically,the Pacific inflow temperature in the Bering Strait and Atlantic inflow temperature in the Fram Strait hit record highs,while the Pacific inflow salinity in the Bering Strait and Arctic outflow salinity in the Davis and Fram straits hit record lows.Both the ocean heat convergence from lower latitudes to the Arctic and the hydrological cycle connecting the Arctic with Subarctic seas were stronger in 2000-2020 than in 1980-2000.CMIP6 models project a continuing increase in poleward ocean heat convergence in the 21st century,mainly due to warming of inflow waters.They also predict an increase in freshwater input to the Arctic Ocean,with the largest increase in freshwater export expected to occur in the Fram Strait due to both increased ocean volume export and decreased salinity.Fram Strait sea ice volume export hit a record low in the 2010s and is projected to continue to decrease along with Arctic sea ice decline.We quantitatively attribute the variability of the volume,heat,and freshwater transports in the Arctic gateways to forcing within and outside the Arctic based on dedicated numerical simulations and emphasize the importance of both origins in driving the variability.