Sea surface salinity as a proxy for Arctic Ocean freshwater changes

The changing Arctic freshwater content and distribution have significant implications for ocean circulation, climate, and water and biogeochemical cycles. The paucity of in-situ salinity measurements in the Arctic Ocean has limited our ability to study Arctic-Ocean freshwater variability. Although satellite-derived sea surface height (SSH) and ocean bottom pressure (OBP) have been used together to infer depth-integrated freshwater content changes, these measurements are limited in sampling and resolution. Motivated by the recent development of sea surface salinity (SSS) remote sensing, we explore the use of SSS as a proxy for Arctic freshwater changes. As a first step, here we conduct a proof-of-concept study by analyzing the output of an ocean-ice state estimation product. We find that SSS variations are coherent with those of SSH-minus-OBP across the Arctic basin (with R ~ -0.8) except for in the center of the Beaufort Gyre and the region affected by the subpolar North Atlantic inflow. On Arctic shelves, the linear regression coefficient between SSS and SSH-minus-OBP is -0.3 pss/cm or larger in magnitude. The results suggest that SSS is a good proxy for Arctic freshwater changes, and satellite SSH-minus-OBP can be used to evaluate satellite SSS quality.