Validation of OSCAR Surface Currents in the Western Arctic Marginal Seas
against Saildrone Observations
Abstract
The 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
(USVs) 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 with significant noise. Higher vector correlation and
speed difference often occur where stronger currents (often
topography-steered) are observed. Such differences reveal that the
dataset 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.