Physical Oceanography (Feb 2023)
Eddies in the Norwegian and Greenland Seas from the Spaceborne SAR Observations in Summer, 2007
Abstract
Purpose. The paper is aimed at analyzing the spatio-temporal variability of eddy field in the ice-free regions of the Norwegian and Greenland seas in summer, 2007 based on processing the spaceborne synthetic aperture radar (SAR) data, and its dependence on the background wind conditions and the surface current field. Methods and Results. The Envisat ASAR radar images (RI) obtained in the WSM imaging mode with the 400 × 400 km swath width and the 150 × 150 m spatial resolution for May – October, 2007, were used as the initial data. The eddy surface manifestations were identified by an expert through the visual analysis of RI, after which the eddy diameter and rotation sign, as well as the total depth of the place corresponding to the eddy center, were determined. Information on the near-surface wind field was derived from the CMEMS WIND_GLO_PHY_CLIMATE_L4_REP_012_003 product based on the ASCAT scatterometer measurements carried out with the 0.25° spatial resolution. To analyze the relation between the eddy generation intensity and the surface currents’ background field at the 1 m depth, the CMEMS GLORYS12V1 oceanic reanalysis with the 0.25° spatial resolution was applied. In total, more than 3000 surface eddy manifestations were recorded. The key regions where the eddies were observed and which were characterized by the eddies’ maximum probability, were found over the Norwegian continental shelf east of the Vøring Plateau (water depth < 200 m), on the eastern slope of the Lofoten Basin, in the western part of the Denmark Strait and over the Iceland-Faroe Ridge. It is shown that the numbers of the observed cyclonic and anticyclonic eddies were equal. The observed eddies’ diameters ranged within 0.5–150 km with the average value of ~ 14 km. Most often the eddies were observed over the depths not exceeding 500 m. The majority of eddy manifestations were identified under the northerly and northeasterly winds of 3–5 m/s and at the boundaries of currents whose velocities exceeded 0.3–0.4 m/s. Conclusions. The number of cyclonic and anticyclonic eddies was recorded equal, which was comparable to the results of altimetry observations in the region, but differed from the results of SAR observations in the other Arctic and sub-Arctic regions where the cyclonic eddies dominated. The observed eddies were most often detected along the main jet currents and in the regions of their meandering.
