Snowy days have decreased substantially in Estonia

In the end of December 2019, there was no snow in Tartu. Instead, liverworts (Anemone hepatica) were blooming at the UT Botanical Garden. Image credit: Inga Külmoja

Geographers of the Institute of Ecology and Earth Sciences of the University of Tartu have released a study indicating that the snow situation in Estonia has substantially changed in the last decades. While our grandfathers and grandmothers could often sled in the beginning of April as children, the kids of today can put away their sleds in the middle of March. There’s just no snow.

Air temperature has risen by two degrees

Snow cover depends on the air temperature. It lasts when the temperature is near zero, which is quite characteristic of the climate in Estonia. As the average air temperature has significantly risen in Estonia during the last decades — nearly two degrees, compared to the post-war years — it’s natural that there has also been a noticeable decrease in snow cover. Presuming that the climate keeps getting warmer, analyzing changes that have taken place allows for making trustworthy forecasts about the condition of snow cover in the future.

Snow thickest at the end of winter

On average, the seasonal dynamics of snow thickness have been such that starting in December, the snow cover becomes thicker and thicker, reaching the maximum at the end of February and at the beginning of March. After this, in the second half of March or at the beginning of April, the snow would melt rapidly. The study proved that the duration and thickness of snow cover vary, depending on the area and the year. Estonian coastal areas, especially the west coast of Saaremaa, have seen significantly lesser duration of snow cover than the rest of Estonia. Snow has covered the ground the longest in the upland of southeastern Estonia and the inland of northern Estonia.

Snow melting earlier in spring

Data from the time series of Estonian weather stations shows that at 16 stations of 22, the duration of snow cover has decreased substantially. It is mostly caused by the snow melting earlier in spring. In 66 years, the period of snow cover in Estonia has decreased 27 days on average. Changes in the beginning and end of the period of continuous snow cover are interesting as well – the beginning of continuous snow cover is just a little late in many places, but the spring melting of snow has shifted 10–30 days earlier over 66 years. Data from these 66 years shows that from the middle of January to the middle of March, the snow cover has become significantly thinner in Estonia: the thickness has decreased 2–9 cm on average during the whole period.

A longer version of the story was published in the science news portal Novaator.

Marko Mägi is a Research Fellow in Bird Ecology and the Head of Communication at the University of Tartu Institute of Ecology and Earth Sciences.

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