Intercomparison of Salinity Products in the Beaufort Gyre and Arctic Ocean

Sarah B Hall,James H Morison,Bulusu Subrahmanyam

doi:10.3390/rs14010071

Abstract

Salinity is the primary determinant of the Arctic Ocean’s density structure. Freshwater accumulation and distribution in the Arctic Ocean have varied significantly in recent decades and certainly in the Beaufort Gyre (BG). In this study, we analyze salinity variations in the BG region between 2012 and 2017. We use in situ salinity observations from the Seasonal Ice Zone Reconnaissance Surveys (SIZRS), CTD casts from the Beaufort Gyre Exploration Project (BGP), and the EN4 data to validate and compare with satellite observations from Soil Moisture Active Passive (SMAP), Soil Moisture and Ocean Salinity (SMOS), and Aquarius Optimally Interpolated Sea Surface Salinity (OISSS), and Arctic Ocean models: ECCO, MIZMAS, HYCOM, ORAS5, and GLORYS12. Overall, satellite observations are restricted to ice-free regions in the BG area, and models tend to overestimate sea surface salinity (SSS). Freshwater Content (FWC), an important component of the BG, is computed for EN4 and most models. ORAS5 provides the strongest positive SSS correlation coefficient (0.612) and lowest bias to in situ observations compared to the other products. ORAS5 subsurface salinity and FWC compare well with the EN4 data. Discrepancies between models and SIZRS data are highest in GLORYS12 and ECCO. These comparisons identify dissimilarities between salinity products and extend challenges to observations applicable to other areas of the Arctic Ocean.

Highlights

Arctic Ocean salinity is a key element of seasonal and interannual variability [1]
The Arctic Ocean serves as a connection between the less saline North Pacific Ocean and the more saline North Atlantic Ocean, and these contrasting salinity characteristics determine the dominant structure of the Arctic Ocean Freshwater Content (FWC)
The local salinity details can be quite different among the products

Summary

Introduction

We provide a comparison regarding modeled, remotely sensed, and directly observed salinity in the Arctic Ocean. We wished to learn the validity of remotely sensed and modeled salinity compared to in situ observations. This, combined with the facts that surface buoyancy fluxes resulting from sea ice formation and melt are due overwhelmingly to salt flux, and that the inflows to the Arctic Ocean are characterized by large differences in salinity, results in the Arctic Ocean being a salt-stratified sea. The Arctic Ocean is a critical link in the global freshwater–thermohaline chain, where the high salinity Atlantic Water combines with less saline Pacific Water and runoff from drainage basins extends south beyond the Arctic Circle. While salinity is important, owing to the ice cover and remoteness, it is extremely difficult to make in situ observations of salinity in critical areas of the Arctic

Results

Discussion

Conclusion