Abstract
Hudson Bay (HB) is the largest semi-inland sea in the Northern Hemisphere, connecting with the Arctic Ocean through the Foxe Basin and the northern Atlantic Ocean through the Hudson Strait. HB is covered by ice and snow in winter, which completely melts in summer. For about six months each year, satellite remote sensing of sea surface salinity (SSS) is possible over open water. SSS links freshwater contributions from river discharge, sea ice melt/freeze, and surface precipitation/evaporation. Given the strategic importance of HB, SSS has great potential in monitoring the HB freshwater cycle and studying its relationship with climate change. However, SSS retrieved in polar regions (poleward of 50°) from currently operational space-based L-band microwave instruments has large uncertainty (~ 1 psu) mainly due to sensitivity degradation in cold water (<5°C) and sea ice contamination. This study analyzes SSS from NASA Soil Moisture Active and Passive (SMAP) and European Space Agency (ESA) Soil Moisture and Ocean Salinity(SMOS) missions in the context of HB freshwater contents. We found that the main source of the year-to-year SSS variability is sea ice melting, in particular, the onset time and places of ice melt in the first couple of months of open water season. The freshwater contribution from surface forcing P-E is smaller in magnitude comparing with sea ice contribution but lasts on longer time scale through the whole open water season. River discharge is comparable with P-E in magnitude but peaks before ice melt. The spatial and temporal variations of freshwater contents largely exceed the remote sensed SSS uncertainty. This fact justifies the use of remote sensed SSS for monitoring the HB freshwater cycle.
Highlights
This study investigates the seasonal and interannual variations of satellite-measured sea surface salinity (SSS) in the Hudson Bay (HB) in the context of HB freshwater contents from river discharge, sea ice melt/freeze, and surface freshwater forcing
We focus on the Hudson Bay proper, which is divided into three sub-regions according to the river water path and HB circulation pattern [10]: the James and eastern Hudson Bay (James_EHB, green color), which is along the path of discharge from southern rivers; the Hudson Bay interior (HB_interior, cyan color) which has negligible direct input from rivers; the Western HB boundary (WHB_boundary, orange color) which is under the influence of river discharges west of HB
This study examines the potential of SSS retrieved from currently operational L-band missions: NASA’s Soil Moisture Active Passive (SMAP) and European Space Agency (ESA)’s Soil Moisture and Ocean Salinity (SMOS), in monitoring the surface freshwater in the Hudson Bay
Summary
This study investigates the seasonal and interannual variations of satellite-measured sea surface salinity (SSS) in the Hudson Bay (HB) in the context of HB freshwater contents from river discharge, sea ice melt/freeze, and surface freshwater forcing (i.e., precipitation minus evaporation). North Atlantic Ocean through two main gateways: the Foxe Basin and the Hudson Strait. The Foxe Basin, with a shallow depth ~40 m and ice-dominated, provides HB with the low salinity water originated at the Arctic Ocean. Along the southern HS, low salinity water of HB is exported to the Atlantic Ocean via the Labrador Sea, providing the third largest source of freshwater to the North Atlantic Ocean after Fram Strait and Canadian Arctic Archipelago. The deep convection in the Labrador Sea supplies intermediate and deep waters to much of the North Atlantic Ocean. It has an indirect effect on the oceanic “conveyer belt” [6]. Monitoring the variability of HB freshwater distribution is important to HB local ecosystem, and contributes to our understanding on the global effect of arctic water outflow
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