Surprising discovery about Svalbard's largest glacier

Researchers at Norsk Polarinstitutt (the Norwegian Polar Institute) have concluded that warm seawater is the chief cause of melting at Bråsvellbreen (Austfonna). It is the biggest glacier in the Svalbard archipelago. Until now, a warmer atmosphere was believed to play a large part in the loss of ice there. The new findings point instead to the ocean as the force working on the glacier front. Marine scientist Øyvind Foss described the result as a surprise.

The team reports that fast melting has been recorded even in October and November. Svalbard is dark in those months, and air temperatures can fall to -20 °C. Glaciologist Geir Moholdt told the Barents Observer that the ocean holds heat better than the air. He said it can stay warm well into autumn, which leads to melting and to calving at glacier fronts. According to him, glaciers in places such as Svalbard, the Canadian Arctic and Alaska, leaving out the ice sheets of Greenland and Antarctica, together account for 20% of present sea level change.

The study drew on three kinds of data. An instrument was left underwater for about four years to record currents and temperatures at several depths. Weather stations on Svalbard supplied readings of air temperature, snow depth, wind and radiation. Satellite images showed the glacier sending ice into the sea faster than in earlier years.

The researchers describe a feedback loop in which each process strengthens the other. Moholdt said that the Barents Sea heats up more quickly because it has less sea ice than before. Ice reflects much sunlight, while open water is darker and takes in more of it. He also said that warm Atlantic water flowing in adds to the heating around Svalbard.

More than half of Svalbard is now glacier-covered. Many glaciers have become thinner by tens of metres and have pulled back several kilometres into the sea. Moholdt said that over the past two decades Svalbard glaciers have shed up to 5% of their total mass. Asked what ordinary people can do, Moholdt said that emissions of greenhouse gases, chiefly CO 2 and methane, can be cut.