Spatial and Temporal Variability of the Characteristics of the River Plume Frontal Zone in the Kara Sea in the First Two Decades of the XXI Century

The article is devoted to obtaining long-term physical and geographical characteristics of the River Plume frontal zone as a separate hydrological structure that forms at the boundary of the fresh surface layer of the Ob and Yenisei Rivers. The primary data for identifying the frontal zone are satellite measurements of surface temperature (MODIS Aqua, Suomi NPP-VIIRS), surface salinity (NASA SMAP) and sea level (AVISO) for the period from July to October from 2002 to 2020. The position and characteristics of the River Plume frontal zone were determined using cluster analysis, which was applied for the first time to an integrated set of remote satellite sensing data in this region. The results of the study showed that in the warm period of the year, the average long-term surface temperature gradient of the River Plume frontal zone was 0.08 °C/km, the surface salinity gradient was 0.1 PSU/km, and the area was 155,000 km2. During the ice-free period of the second decade of the 21st century, the temperature gradient of the frontal zone weakens by 0.04 °C/km, and the area decreases by 100,000 km2. The correlation analysis showed that the temperature and salinity gradients, as well as the area of the River Plume frontal zone, were determined by the volumes of the river discharge of the Ob and Yenisei and ice parameters in the warm period of the year. The article presents the obtained estimates of the relationship between the characteristics of the frontal zone and the volume of river discharge, ice cover and wind parameters, as well as the value of the atmospheric indices of the Scandinavian oscillation (SCAND).