Validation of OSCAR Surface Currents in the Western Arctic Marginal Seas Against Saildrone Observations

Abstract

AbstractThe western Arctic marginal seas undergo large seasonal variation, but are very challenging to observe directly due to sea ice and shallow depths. Deployments of several saildrone uncrewed surface vehicles in the summers of 2018 and 2019 provided unique opportunities to validate the satellite‐derived near surface currents, Ocean Surface Current Analysis Real‐time (OSCAR), in the western Arctic marginal seas against in situ upper ocean current measurements. Overall, OSCAR current is biased low (by 5.3 cm/s) with significant noise. Higher vector correlation estimated by the cosine similarity and speed differences often occur where stronger currents (often topography‐steered) are observed. Such differences reveal that the data set resolvability depends on spatial and temporal resolutions, smoothing, and latitudes, suggesting that OSCAR is able to depict the major current systems but significantly underestimates their strength. Poorer vector correlation occurs at weaker current regimes (<10 cm/s), over the shallow Hanna Shoal, near fresher water due to ice melt and river discharge. The latter two water class regimes highlight the importance of salinity contribution to the buoyancy force which is neglected in the OSCAR formulation.