MOSCOW, July 21. /TASS/. Experts of the Tomsk State University found a significant accumulation of greenhouse gases (carbon dioxide and methane) in Western Siberia's reservoirs in winter, and they vigorously break through to the surface during the spring ice retreat. Press service of the Ministry of Science and Higher Education reported the research results.
"The Tomsk University's scientists, supported by the Russian Science Foundation, conducted a big-scale study of the concentration of carbon - the main component of greenhouse gases in Western Siberia's reservoirs," the press service said. "The region's main feature is the harsh continental climate with long winters. Until now, processes under the ice have remained a mystery to science. The researchers supposed that winter is a period of gases accumulation, and the spring ice meltdown provokes a sharp release of carbon accumulated over the cold season. The research results are published in the Journal of Hydrology."
Samples, measurements, and seasons
According to the project's leader, Sergey Vorobyov, who is director of the university's Megaprofile Center for Collective Use, scientists selected water bodies of various sizes to test the hypothesis - from tiny temporary puddles of less than 100 square meters to big lakes of more than one square km. The scientists sampled water and gas concentrations four times a year: in summer, in autumn before freezing, in winter under the ice, and in spring immediately after the ice melting.
"The tests showed a clear dependence of water's chemical composition and the intensity of gas exchange on the water mirror area. Like we have assumed, small pools turned out to be most chemically active. This is due to their close relations to the surrounding peat bogs. Spring meltwater washes out a big amount of organic matter and elements from moss and last year's fall, turning these puddles into real 'biochemical reactors,' where we have recorded highest concentrations of dissolved carbon and nutrients," the scientist said.
Big lakes, on the contrary, have a more stable composition, resembling regular northern lakes. Water there is less acidic. It contains less organic matter and is more susceptible to the influence of groundwater.
Ice as a filter
"The key discovery was that we have confirmed the winter accumulation mechanism. Under the ice, the concentration of carbon dioxide and methane used to increase by spring. At the same time, ice acts as a filter: some elements (for example, fluorine and boron) get accumulated in the remaining water, while others (calcium, strontium), on the contrary, are part of growing ice crystals. When spring comes and the ice breaks, there happens a massive release of gases into the atmosphere," Bogdan Mikhailenko of the university's BioGeoClim Laboratory said.
By having analyzed obtained data, the scientists predicted annual greenhouse gas emissions in the test area - the northern spurs of the Bolshoy Vasyugansky Swamp, which in the south is bounded by the main Bolshoy Vasyugansky Swamp, and in the north - by the Ob River's left bank. Even ignoring the winter greenhouse surge, the researchers found that reservoirs with an area of more than 0.1 square km accounted for the biggest total contribution to total emissions of carbon dioxide and methane from the peat complex. They supplied up to 72.5 kg of carbon per year in the form of carbon dioxide and 58.4 kg of carbon per year in the form of methane.
According to the obtained data, in late winter, after the ice opening, carbon dioxide emissions may increase by 7-8 times, and methane emissions - by more than ten times. Within one winter, there may be more accumulated greenhouse gases that within all other seasons.
Counterbalance to mechanical accumulation
Results of the research, which covered a complete annual cycle, authors say, change the understanding of the role Siberian marshes are playing in the Earth's climate system. The scientists found that peat lakes and temporary puddles inside swamps are not just passive water reservoirs. They are effective "valves" that regulate over a year emissions of carbon dioxide and methane into the atmosphere.
Peat lakes counterbalance the carbon accumulation process, turning the swamp from a pure sink into a complex system with intensive internal circulation and greenhouse gas emissions.
The program featured both experienced scientists and undergraduates studying Siberia and Arctic.