May 9, 2014

The biggest glacier (by size) in Europe is now draining into the Barents Sea at a rate 10 times as fast as it was just a few years ago, according to data collected by a new Earth-observation satellite. The glacier, the Austfonna icecap on Svalbard, had been relatively stable for some decades. (Icecaps are glaciers that cover an area of 19,300 square miles (50,000 square kilometers) or less. Larger glaciers are called ice sheets.) Svalbard is a group of islands in the Arctic Ocean, about midway between Norway and the North Pole. The Earth-observation satellite is the Sentinel-1A, an advanced radar satellite launched last month by the European Space Agency. Scientists with the Sentinel project described the change in the icecap’s speed as “extraordinary.” At this point, they are not certain whether the speed-up is the result of natural changes in the movement of the icecap or a sign of global warming in the Arctic.

The Austfonna icecap covers more than 3,000 square miles (8,000 square kilometers) of Nordaustlandet, the second-largest island in the Svalbard archipelago. Ice from the glacier drains into the sea mainly though a so-called outlet glacier along the southeastern coast of the island. An outlet glacier is a section of an icecap or ice sheet that moves faster than the ice around it.

The chief outlet glacier of the Austfonna icecap (shown in box) is flowing into the sea at least 10 times as fast as it was only a few years ago. (ESA/DLR/Gamma/University of Leeds/University of Edinburgh)

The melting of land-based glaciers is one of the two main causes of the 8-inch (210-millimeter) average rise in global sea levels that occurred between 1880 and 2009.  The other major cause is thermal expansion caused by the warming of the oceans (water expands as it warms). According to one expert involved with the project, icecaps and glaciers contain only 1 percent of the world’s ice. But they have contributed about 50 percent of modern sea-level rise due to ice melting. Glaciers flow slowly under the influence of gravity. If the amount of new snow that accummulates on the glacier is about the same as the amount of the glacier’s ice melting into the sea, the glacier is considered stable.

Additional World Book articles:

• Ice formation
• The Great Meltdown (a Special Report)