Purpose. The study is purposed at analyzing spatial and temporal climatic variability of the upper mixed layer in the Barents and Kara seas on a climatic scale.
Methods and Results. Potential water density is calculated based on the ORAS5 reanalysis data on the average monthly values of potential temperature and salinity at the nodes of a grid of about 10 km with an irregular step over vertical up to a depth of about 400 m for the 1958–2022 period. The formed density array makes it possible to determine the upper mixed layer thickness in the Barents and Kara seas. Threshold criterion Δσ = 0.03 kg/m3 is used for its estimation. The obtained results permit to identify the areas notable for significant variability of the upper mixed layer thickness.
Conclusions. The analysis shows that the upper mixed layer maximum development falls on February and March, whereas the minimum one – on June and July. Thus, the highest values of the upper mixed layer thickness are observed in the seas under consideration during increased autumn-winter convection. In the cold half of a year (November – April), the upper mixed layer thickness averages 105 m in the Barents Sea and 23 m in the Kara Sea. The analysis of interannual variability of the average annual thickness values of these layers shows the presence of a positive climatic trend, i. e. a thickness increase in the upper mixed layers in the Barents and Kara seas in 1958–2022. The upward trend is observed both in the cold and warm halves of a year. The values of average annual thickness trends of the upper mixed layers in the Barents and Kara seas average 1.3 m/10 years and 1.2 m/10 years, respectively.