Increase of density due to mixing (cabbeling instability) in a spring thermal bar in Lake Baikal results in the sinking of cold surface water (T = 3.2−3.4°C, w = 0.3 cm s−1) below the profile of Tmd. This density increase generates forced convection and subsequent movement of cold water along the underwater slope to maximum depths. Cooling of deep and near‐bottom waters caused by forced convection is compensated during other seasons of the year by eddy heat flux directed toward the bottom. On a long‐term basis, vertical temperature profiles in deep waters remain constant.

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We give an overview of the history of the ice cover studies in Lake Baikal and a detailed description of the temporal and spatial variability of Lake Baikal ice conditions based on satellite and historical data. We analyze the long-term evolution of ice conditions using historical data and recent observations from satellite altimetry and radiometry for 1992-2004 for northern, middle, and southern Baikal. These data show a recent (since the 1990s) tendency for colder winters, with earlier ice formation, later ice break-up, and ice duration increase. These observations are in agreement with the long-period cycles of air temperature variability (warming between the 1970s and 1990s, with a cooling phase afterwards). We then compare air temperature data from meteorological stations to ERA-40 reanalysis and suggest that ERA-40 data can be used to assess seasonal and interannual changes of air temperature for Lake Baikal. The ERA-40 data also indicate a recent tendency for colder winters and for warmer summers. We further analyze how the ice regime is influenced by air temperature and how this influence is affected by dynamic (wind field, currents) and other (bathymetry, precipitation, etc.) factors. We estimate the relationship between air temperature parameters and the timing of ice events (ice formation and fast ice duration) and show that air temperature has the strongest effect on the ice regime. Dynamic and other factors interfere with the thermal influence, resulting in a change of ice formation dates and ice duration compared to the relationship that takes into account only the influence of air temperature.