Origin and evolution of the surface desalinated layer of the Kara Sea during the ice-free period

This work focuses on the freshwater contribution (water from the Ob’ and Yenisei rivers and ice meltwater) to the surface layer of the Kara Sea according to 2015–2020 expedition data. Salinity and hydrochemical data (total alkalinity and silicates) were used to calculate the proportion of freshwater in the desalinated layer of the Kara Sea. The ratio of the water fractions with the linear mixing of several sources was considered. Our results showed that riverine sources varied greatly, and the total contributions of the Ob’ and Yenisei runoff ranged from 10 to 60%, while the contribution of ice meltwater did not exceed 25%. The relationship between the period of seasonal ice retreat in the Kara Sea and its proportion in the surface desalinated layer was revealed. The interannual variability in freshwater source composition varied greatly from the southwestern to the eastern part of the sea owing to wind forcing and seasonality in river discharge.