Changes, which took place in a unique ecosystem of Lake Baikal, have always attracted scientists. Heating of Baikal water column was of extreme interest – climate warming near the lake was two times faster than average values for any place on the globe.

Warming of climate, which is observed during recent decades, has heated upper layers of Baikal water, but had no effect on its deep waters, Russian limnologists, who perform long-term measurements of the lake’s water temperature at various depths, report. Between 1970 and 1995 average air temperature near the south edge of the lake added 2.3 °Ñ, as for surface water temperature during warm season, which is May-September, it is now 1.3°Ñ higher than it used to be.

The problem has another aspect – at significant depths temperature of maximum water density changes, hence, response of temperature of upper and lower water layers on climate warming may vary. In upper water layer, which are not deeper than 300 meters, water exchanges heat with atmosphere and thermal convection causes vertical mixing of water column twice a year – in spring and in autumn. Deeper layers of Baikal waters change temperature due to forced sinking of waters from upper layers, caused by dynamic processes. In autumn cold waters from the surface get to the lake’s bottom, but when the weather is warm, heat also gets down due to turbulence.

 

 

Russian researchers measured water temperature at various depths and in various parts of the lake between 1972 and 2007. First twenty years measurements were taken more often – during summer heating, autumn cooling and winter temperature minimum, and after 1992 water temperature was measured only during summer periods. However, in layers, located deeper than 4000 meters, average values of water temperature showed good correlation, thus researchers calculated water temperature for the whole year, using figures thy got during summer observations.

Experiment allowed researcher to conclude that surface water temperature has grown significantly during recent decade, being especially high in summers. Average water temperature of the 0-300 meter layer for the period of June-December added 0.05-0.07°Ñ every ten years.

However, deep waters of lake Baikal showed no significant changes in temperature, but researchers detected interannual temperature variability of deep water layers with period of 6-10 years and amplitude of 0.07-0.1°Ñ in 200-400 meter layer, 0.06-0.07°Ñ in 400-600 meter layer, and up to 0.03-0.06°Ñ in deeper waters. Scientists tend to explain this phenomenon with wind, which speed has a great effect on dynamic atmospheric impact on water column. Experiment showed a strong inverse relationship of water temperature and wind speed in December-January and May-June periods.

Therefore, Baikal waters, which are not deeper than 300 meters, react on atmosphere’s heat impact by heating, when that air gets warmer. Temperature of deep water layers mainly depends on dynamic effects atmosphere has on water. Wind mixes water, and temperature fluctuations are caused by warm or cold water from the surface.

Source: Science & Technologies

Kizilova Anna