Interannual Variability of Surface Salinity and Ekman Pumping in the Canada Basin During Summertime of 2003-2017

The Canada Basin (CB) is undergoing significant changes due to long-term global climate change, and other shorter time-scale processes that are still not well understood. Based on the in-situ and satellite observations and atmospheric reanalysis data, interannual variabilities of sea surface salinity and Ekman pumping in the CB are investigated in the summertime of 2003-2017. This study reveals strong surface salinity reduction and Ekman downwelling enhancement during 2006-2012 compared with the remaining years. The surface 20-m salinity averaged in 2006-2012 decreases by 1.26 PSU relative to the other years. The results suggest that the lower surface salinity is correlated to enhanced sea ice melt and Ekman convergence in the CB. Enhanced downward solar radiation accounts for the accelerated sea ice melt over the southeast CB, leading to the surface salinity decrease. Strengthened anticyclonic wind circulation over the CB not only enhances sea ice melt via strengthening offshore Ekman transport over the Chukchi Sea slope, but also favors freshwater accumulation in the CB through strengthening the horizontal convergence. The sea ice melt is estimated to account for 54% of the surface freshening, and the horizontal convergence is believed to play an important role in the remaining 46%. During the freshening years in the CB, the Ekman downwelling enhancement is mainly attributed to variations of wind stress curl, sea ice concentration, and ice-ocean stress curl, and their relative contributions are estimated on the basis of on a linearized model as 72%, 12%, and 10%, respectively. Plain Language Summary The Canada Basin (CB) is undergoing significant changes due to complicated interactions between air, sea ice, and ocean. The atmospheric high-pressure system over the CB accumulates the surface freshwater into the CB center due to the Coriolis effect. The accumulation leads to a relatively low salinity and downward currents in the CB. The observations during the summertime of 2003-2017 reveal interannual variabilities of the surface salinity and the downwelling in the CB. The surface salinity is remarkably decreased, and the downwelling is strengthened in 2006-2012 compared with those of the other years. The analysis based on the oceanic and atmospheric data here demonstrates that these variabilities are mainly attributed to variations of wind circulation and sea ice.

Automated summary

Observations during the summer seasons of 2003-2017 reveal significant interannual variabilities in surface salinity and Ekman downwelling in the Canada Basin (CB), with pronounced decreases in surface salinity and strengthened downwelling dynamics observed during 2006-2012 compared to other years, mainly attributed to changes in wind circulation and sea ice behavior.