Russian Journal of Earth Sciences Russian Journal of Earth Sciences Russian Journal of Earth Sciences 1681-1208 46520 10.2205/2020ES000700 ОРИГИНАЛЬНЫЕ СТАТЬИ ORIGINAL ARTICLES ОРИГИНАЛЬНЫЕ СТАТЬИ Tracking the formation of the gradient part of the southeastern Baltic Sea cold intermediate layer Tracking the formation of the gradient part of the southeastern Baltic Sea cold intermediate layer Stepanova N Stepanova N stepanova.nb@ocean.ru Mizyuk A Mizyuk A Shirshov Institute of Oceanology RAS and Institute of Physics and Technology, Dolgoprudny ru Shirshov Institute of Oceanology RAS and Institute of Physics and Technology, Dolgoprudny ru Marine Hydrophysical Institute RAS ru Marine Hydrophysical Institute RAS ru 20 3 1 11 29 10 2021 https://rjes.ru/en/nauka/article/46520/view

In order to study the peculiarities of the thermohaline structure of the Baltic Sea, we conducted a research based on the Copernicus Marine Environment Monitoring service (https://marine.copernicus.eu/) products and field data collected in 2004-2006. The study of the reanalysed Baltic Sea hydrography allows us to show that it adequately reproduces elements of the thermohaline structure of the cold intermediate layer obtained from the measurement data. Here we examine the hypothesis about the formation of a lower part of the cold intermediate layer in early spring under the influence of a mechanism related to the estuary salinity/density gradient along the main axis of the Baltic Sea. Several numerical experiments were carried out to analyse the back trajectories of Lagrangian particles in the southeastern Baltic Sea. The analysis showed that in the Gdask Basin, at the depth corresponding to the lower part of the cold intermediate layer, there are particles coming from the Bornholm Basin and the S{upsk Channel. This confirms the contribution of the estuary salinity gradient to the formation of the lower part of the cold intermediate layer.

In order to study the peculiarities of the thermohaline structure of the Baltic Sea, we conducted a research based on the Copernicus Marine Environment Monitoring service (https://marine.copernicus.eu/) products and field data collected in 2004-2006. The study of the reanalysed Baltic Sea hydrography allows us to show that it adequately reproduces elements of the thermohaline structure of the cold intermediate layer obtained from the measurement data. Here we examine the hypothesis about the formation of a lower part of the cold intermediate layer in early spring under the influence of a mechanism related to the estuary salinity/density gradient along the main axis of the Baltic Sea. Several numerical experiments were carried out to analyse the back trajectories of Lagrangian particles in the southeastern Baltic Sea. The analysis showed that in the Gdask Basin, at the depth corresponding to the lower part of the cold intermediate layer, there are particles coming from the Bornholm Basin and the S{upsk Channel. This confirms the contribution of the estuary salinity gradient to the formation of the lower part of the cold intermediate layer.

 Cold intermediate layer vertical stratification basin-scale exchange thermohaline structure the Baltic Sea Lagrangian transport Cold intermediate layer vertical stratification basin-scale exchange thermohaline structure the Baltic Sea Lagrangian transport The authors are grateful to many scientists and organizations which perform measurements and maintain data exchange network in the Baltic Sea region. In particular, the data of the LUKOIL monitoring program (cruises of R/V Professor Shtokman) were kindly provided for scientific research by KaliningradMorNeft, and the data from the Arkona Basin Buoy - by the Federal Maritime and Hydrographic Agency (http://www.bsh.de). Collection, processing and analysis of field data were performed within the State Task 0149-2019-0004. Backtracking and comparative analysis of numerical results and field data was carried out with the support of the Russian Foundation for Basic Research (grant No. 18-35-00453).

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