| Summary: | Purpose. Frontal zones are the areas of strong horizontal gradients of physical, chemical and biological parameters that have a significant impact on the dynamics of the Global Ocean. The aim of the paper is to study the spatial and vertical distribution (including seasonal and interannual variability) of frontal zones in the Norwegian Sea. Methods and Results. The data on temperature, salinity, sea surface height and velocities from the GLORYS12V1 reanalysis for 1993–2019 available on the CMEMS (Copernicus Marine Environment Monitoring Service) resource, were used. Five mesoscale frontal zones in the area under study were identified, and the average and maximum gradients in the temperature, salinity and sea surface height fields were calculated. The maps of spatial distribution of the thermohaline and dynamic frontal zones, and also of the frequency of frontal zones were constructed. The correlation between the atmospheric indices NAO (North Atlantic Oscillation) and AO (Arctic Oscillation), and the temporal and interannual variability of the frontal zone areas was assessed. Conclusions. It is shown that the thermohaline and dynamic gradients observed in winter are on the average higher than those observed in summer. It is found that increase of depth is accompanied by a shift of the frontal zones towards the Lofoten Basin and the Faroe-Iceland threshold. The frontal zones frequency maps demonstrate a high rate (≥ 50%) of the areas with strong gradients near the Lofoten Vortex, Svalbard, the Mohn Ridge and the Norwegian continental slope. The majority of frontal zones are of well pronounced seasonal and interannual variability. A negative interannual correlation is noted between the frontal zones areas and the NAO and AO indices. It is also shown that seasonal variability is in high positive correlation with NAO.
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