Variability of the East Greenland Current in Fram Strait From Subdaily COSMO-SkyMed X-SAR Imagery

Abstract

Sea ice speed vectors were extracted from COSMO-SkyMed X-band SAR images acquired twice per day from March 2013 to December 2014 over the East Greenland current (EGC) in western Fram Strait. Only winter periods (October-May) were investigated. Maximum ice speed of 81.7 cm/s to SW was detected at 80°N 0°W between November22 and 23, 2013. At 79°N between 7° and 5°W, sea ice speed vectors were mostly directed to S-SW but reversed to the north for short periods. Using ERA-Interim atmospheric data, the southward component of the ice speed (max. +71.7, min. -30.9 cm/s) was correlated (R = 0.93) to the cross-strait sea level pressure gradient. Ice speeds due to the EGC were obtained by subtracting the wind-induced ice speed component estimated by linear regression. Results for winter 2013-2014 show that the mean southward component of the EGC (9.4 cm/s, σ = 3.0) accounted more than half of the mean sea ice speed (17.7 cm/s, σ = 7.2). The EGC oscillated between 5 and 15 cm/s and sustained the southward ice export during short periods when the wind reversed to north. Satellite-based measurements of the surface EGC are the complement to hydrographic measurements in Fram Strait, but further investigation is required to understand how the apparent variability of the current is influenced by the thickness of the ice transiting in the strait or by wind induced north-to-south oscillations of the sea surface in the strait.