Arctic Summer Sea Ice Extent Affects Winters in Central Europe
03.02.2012 - Atmosphere & Space, Water & Oceans, Ice & Snow, Arctic
Scientists from the Research Unit Potsdam at the Alfred Wengener Institute for Polar and Marine Research (AWI) have been able to connect reduced summer sea ice extent in the Arctic with colder and snowier winters in Central Europe in a study published in the journal Tellus A.
Whenever there is large-scale melt of Arctic sea ice in summer, two important effects become intensified. Firstly, the retreat of the sea ice, which has a high albedo, reveals more of the darker ocean, which absorbs more energy from the sun and heats up. Secondly, with no sea ice to cover the ocean, latent heat in the water is released into the atmosphere, which leads to warmer air in the Arctic during the autumn and winter. Atmospheric temperatures in the Arctic have been warmer over the past several years according to measurements.
Warming air near the Earth’s surface then leads to rising movements in the atmosphere, creating instability. This influences the typical circulation and air patterns, including the air pressure difference between the Arctic and the mid-latitudes (the Arctic Oscillation with the Azores highs and Iceland lows). If there is a large pressure difference, it results in westerly winds, which carry warm, moist air from the Atlantic towards Europe in the winter. If the difference in pressure is not high and no westerly winds form the Atlantic are generated, then colder, Arctic air can descend into Europe, which was the case during the winters of 2009-2010 and 2010-2011.
Snow cover in Siberia and tropical influences are also linked to winter weather patterns over Europe, according to Ralf Jaiser from AWI, lead author of the study