The mass of seasonal snow cover in Northern hemisphere decreased by 1.5 percent over the past forty years

From 1980 to 2018 average mass of seasonal snow cover in Northern hemisphere decreased by 49 gigatons, which is about 1.5 per cent of its seasonal quantity. Thus, 46 gigatonnes made up the losses in North America and only three gigatons in Eurasia. According to a study published in the journal Nature, the continents show a high spatial heterogeneity of the dynamics of the snow cover: in the Baltic States there has been a continuous gradual decline in the number of snow precipitation, and in Eastern Siberia — their growth.

To track the melting and formation of sea ice, as well as the growth and retreat of ice cover shields play an important role in the climate system of the planet, much easier than to assess the dynamics of the seasonal snow cover. Snow has properties that are detrimental for high-precision monitoring: a pronounced spatial heterogeneity (for short time periods on the adjacent territories the snow can be wet or loose, and then compacted or covered with a crust of ice) and the uncertainty of depth. Snow cover can increase and thicken, and it does not always lead to a noticeable increase in its area. Climatologists point to this as the main source of uncertainty in the study of its seasonal dynamics.

It is important to achieve more accurate quantitative estimates of seasonal snow, as it plays an important role in the Earth’s climate system: lowers the temperature of the surface layer of air and replenish main resources of fresh water. A large part of the rivers of the Northern hemisphere gets its power by melting of seasonal snows.

Scientists led by Junie Pulliainen (Jouni Pulliainen) from the Finnish Meteorological Institute has studied the long-term dynamics of seasonal snow cover in the Northern hemisphere using GlobSnow v.3.0 — system processing of data obtained from sensors AATSR ERS-2 and ATSR-2 on Board the satellite Envisat. In the study they included land areas North of 40 degrees North latitude and forthe exception of mountain areas and divided them into 5 regions: A(North Europe and the Baltic States), B (Western Siberia), C (Eastern Siberia), D (Western North America) and E (Eastern North America). For processing we used the data on the amount of snow cover in March 1980 to 2018 as of March had the peak of the snowfall.

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