Quality assessment of a satellite altimetry data product in the Nordic, Barents, and Kara seas

Satellite altimetry provides high-quality sea surface height data that have been successfully used to study the variability of sea level and surface geostrophic circulation at different spatial and temporal scales. However, the high-latitude regions have traditionally been avoided due to the persistent sea ice cover. Most of the validation studies have focused on the areas below the polar circles. In this paper we examine the quality and performance of a gridded satellite altimetry product in the Nordic, Barents, and Kara seas. The altimetric sea level in coastal areas is validated using available tide gauge records. We show that at most locations in the Nordic seas the altimetry and tide gauge measurements are in a good agreement in terms of the root-mean square differences and the amplitudes and phases of the seasonal cycle. The agreement deteriorates in the shallow areas of the Barents and Kara seas subject to the seasonal presence of sea ice, and where the altimetry data are contaminated by the residual aliasing of unresolved high-frequency signals. The comparison of linear trends at the locations of tide gauges reveals discrepancies that need to be taken into account when interpreting long-term changes of sea level in the region. Away from the coast the altimetry data are compared to drifter trajectories, corrected for Ekman currents. The drifter trajectories are found consistent with the mesoscale variability of the altimetric sea level. This study provides the first comprehensive validation of a gridded satellite altimetry data product in the high-latitude seas.