The anticyclone accelerated melting of the Greenland ice sheet

Last year, the Greenland ice sheet lost the largest amount of ice in the entire history of measurements of 600 billion tonnes, and thereby increased the Global sea level of half a millimeter. In 2019 there was a change in atmospheric circulation in the polar latitudes, which provoked anticyclonic activity. Currently used climate models do not account for such events and may underestimate the potential melting of the ice masses by 50 percent. The results of a study published in the journal The Cryosphere.

Every year in Greenland there is an increase of ice mass through snowfall and its melting with surface runoff of melt water. Both of these processes occur in parallel and are subjected to careful measurement, and the difference between them is expressed in the form of the surface mass balance of the Greenland ice sheet. Usually the balance is positive: on average, the island is formed of 375 billion tons of ice per year. In 2019 Greenland has lost 600 billion tons of ice, and his net gain was only 50 billion tons — and it is very small, given the constant gathering of icebergs into the ocean.

A similar situation was already observed in 2012, when the Greenland ice sheet lost at 310 billion tons of ice in comparison with the baseline 1981-2010 years. However, the air temperature over Greenland in the year was higher than in 2019. This contradiction brought Marco Tedesco (Marco Tedesco) from Columbia University and Xavier Fatwas (Xavier Fettweis) from the University of liège on the assumption that the previously adopted climate models could underestimate the role of anticyclonic activity for surface mass balance.

Scientists investigated changes in the dynamics of the Greenland ice sheet in 2019. They used satellite estimates of broadband albedo, obtained using the Spectroradiometer moderate resolution MODIS data in the period from 2000 to 2019, and weather data the National weather service of the United States from 1948 to 2019. With their help, managed to restore in detail the melting of the Greenland ice sheet during 2019.

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