Variability of the Polar Frontal Zone Characteristics in the Northwestern Barents Sea Based on In-Situ Observations under Sea Ice Declining Conditions

The results of oceanographic observations conducted on board the R/V “Dalnie Zelentsy” along the Kola Section during 2017–2023 are presented. The main focus is on the assessment of frontal zone characteristics in the northern part of the Polar Front during autumn, winter, and spring periods. To estimate sea ice anomalies, data from the World Data Center for Sea Ice (AARI WDC Sea-Ice) were used. A comparison was made between observational data from the northern section near the Marginal Ice Zone and temperature and salinity characteristics from global oceanographic databases. The comparison involved products such as MERCATOR PSY4QV3R1, CMEMS GLORYS12v1, and TOPAZ5. High-gradient zones in temperature and salinity fields were identified along all sections at varying distances from the ice edge. It was confirmed that the western Barents Sea had experienced a steady trend of sea ice cover declining over the past three decades. The northernmost frontal zone of the Polar Front in the Barents Sea, along the Kola Section axis, detected at distances of 48 to 290 km from the ice edge. Temperature gradients ranged from 0.10 to 0.20 °C/km, salinity gradients varied from 0.012 to 0.025 psu/km, and the width of the frontal zone did not exceed 55 km. The best correlation with the measurement results was observed in for the MERCATOR PSY4QV3R1 product.