CliSAP successfully finished in 2018. Climate research continues in the Cluster of Excellence "CLICCS".

Decline in Arctic sea ice this summer: New negative record becoming apparent


This summer the layer of sea ice on the Arctic is very likely to decline to the record mark reached in 2007, or possibly even fall below this mark. Prof. Dr. Rüdiger Gerdes, sea ice physicist with the Helmholtz Association of the Alfred Wegener Institute for Polar and Marine Research, said at an Arctis workshop in Bremen on Monday that everything pointed to an extremely low extent of ice in September. Based on his statistical analysis, Prof. Dr. Lars Kaleschke of KlimaCampus at the University of Hamburg also expects to see a considerable loss of ice.

"A look at the latest satellite maps shows quite clearly how much ice will still have melted by the middle of September. The edges of the ice layer are broken up to such an extent that solar radiation can now heat up the top layer of water, causing many floes to melt," says Rüdiger Gerdes.


Lars Kaleschke also calls it a photo finish. "Our prediction based on statistics indicates that the decline in ice will almost match that of 2007, only that the ice masses are distributed differently this year," he says. This summer the ice-free areas in the pack ice zone are exceptionally large, for example in the Laptev Sea in northern Russia. "This opening in the layer makes the impression that the ice has melted from below here. It appeared early in August, became gradually larger and is now as big as Holland," sea ice researcher Lars Kaleschke says.


Two factors seem to play a vital role this summer. On the one hand scientists from the Alfred Wegener Institute, who recently advanced to the North Pole on board the research icebreaker Polarstern, report that the sea ice is very thin. Measurements showed that the layer averaged 90 centimetres. By way of comparison: In 2001 the average thickness of the sea ice was two meters.  On the other hand, sea ice is constantly being transported to ice-free regions in the Arctic Ocean. Rüdiger Gerdes explains: "Water temperatures are high there due to irradiation and absorption, so ice floes drifting in the area melt rapidly."


It will, however, not become known before the end of September whether or not the decline in sea ice will actually fall below the record mark reached in 2007. The lowest level ever was reached four years ago, when the extent of ice declined to cover 4.3 million square kilometres.