| Summary: | 2019 Living Planet Symposium, 13-17 May 2019, Milan, Italy This study investigates the sea surface salinity (SSS) observed by the Soil Moisture Active Passive (SMAP) mission (2015-present) and Soil Moisture Ocean Salinity (SMOS) mission (2011-present) in the open water season in the Hudson Bay and its association with the freshwater flux. A unique large inland sea in northern Canada located in the southern margin of the Arctic Circle, the Hudson Bay is covered by ice and snow in winter. Around 1300 km3 low salinity liquid water trapped in ice is completely melt and released in summer. The length of the open water season has been increasing in recent years, allowing more days during which the SSS can be retrieved from satellite microwave radiometer data (from SMAP and SMOS). The SSS reflects and links the impact of freshwater inputs from river discharge, sea ice changes, surface forcing (P-E), and exchange with northern Atlantic Ocean through the Hudson Strait and Arctic Ocean through the Foxe Basin. Both SMAP (JPL V4) and SMOS (BEC) SSS shows a general pattern of freshening in the James and southern Hudson bay, salty in the northern part, and saltier in the Hudson Strait and the Foxe Basin, which are consistent for three years during (2015-2017). However, the SMAP SSS shows some patches of extreme low SSS with large inter-annual variations, particularly early in the melt season; which is missing in SMOS. Dividing the Hudson Bay system into sub-regions, we examine local freshwater inputs in these regions using data of river discharge, sea ice concentration, surface precipitation and evaporation data. We found river discharges and seasonal sea ice changes are the two dominant processes affecting SSS inter-annual variability, but at different time and places; while the surface forcing (P-E) may play a secondary role. Daily discharge rate from the rivers surrounding the Hudson Bay (Canadian EC) was analyzed. We identified that the low SSS in the eastern Hudson and James Bay in August 2015 could be linked with ...
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