Eddy generation in Lake Baikal during ice-free season from satellite remote sensing and field observations

Large Eurasian lakes are an integrator of climate processes at the regional scale and a good indicator of climate changes. Variability of ice and snow regime is important for their physical, chemical and biological properties, and for human activity. 
We address drivers and patterns of eddy generation during ice-free season before and after vertical overturning in lake Baikal (Russia). We use satellite remote sensing, historical observations and in situ data to follow the different stages of warm and cold anticyclonic eddy generation before and after vertical overturning. Thermal satellite images (Landsat-5-7-8) for 1998-2022 indicate a stable repeating seasonal pattern which is classified into stage of eddy generation and development. Field observations complement satellite imagery to characterise the vertical structure of the eddies. The main source of eddy generation of eddies is the outflow from Barguzin Bay which interacts with the coastline. Subsequent eddy generation is driven by density gradients and geostrophic adjustment. In summer this outflow is dominated by river inflow and lead to the formation of warm anticyclonic eddies. After autumnal vertical overturn, the outflow is forced by the wind bringing cold water from the bay to Middle Baikal and creating cold anticyclonic eddies. We suggest that in the autumn, when the surrounding water cools to a temperature below about 4°C, these cold eddies sink and transform into intrathermocline lens-like eddies that persist under ice and can later create giant ice rings on the Baikal ice cover. 
Better understanding of eddy dynamics and continued monitoring help to improve safety for people travelling or working on the ice. There is a need for timely communication of results for non-scientific audience - fishermen, tourism agencies, tourists, journalists and local administration.
This research was supported by the CNES TOSCA Lakeddies, TRISHNA and SWIRL projects, P.P. Shirshov Institute of Oceanology Project N FMWE-2024-0016) and Institute of Water Problems Project N FMWZ-2022-0001.