Arctic sea ice may shrink to record low of 2012

The sea ice cover in the Arctic Ocean this summer may shrink to the record low that was seen in 2012, scientists have warned after evaluating satellite data about the thickness of the ice cover.
The data show that the arctic sea ice was already extraordinarily thin in the summer of 2015. Comparably little new ice formed during the past winter.
Predicting the summer extent of the arctic sea ice several months in advance is one of the great challenges facing contemporary polar research.
Until the end of the melting season, the fate of the ice is ultimately determined by the wind conditions and air and water temperatures during the summer months. Foundations are laid during the preceding winter, however.

This spring, they are as disheartening as they were in the negative record year of 2012. Back then, the sea ice surface of the Arctic shrunk to a record low of 3.4 million square kilometres.
"If we compare the ice thickness map of the previous winter with that of 2012, we can see that the current ice conditions are similar to those of the spring of 2012 - in some places, the ice is even thinner," said Marcel Nicolaus, from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) in Germany.

Researchers evaluated the sea ice thickness measurements taken over the past five winters by the CyroSat-2 satellite for their sea ice projection.

Seven autonomous snow buoys, which the AWI researchers had placed on floes (sheets of floating ice) last year, supplied additional important clues.
In addition to the thickness of the snow cover on top of the sea ice, the buoys also measure the air temperature and air pressure.
A comparison of their temperature data with the long-term measurements showed that the temperature in the central Arctic in February this year exceeded average temperatures by up to 8 degrees Celsius.
This warmth did not result in the thinning of the sea ice cover in some regions over the course of the winter.

"According to our buoy data from the spring, the warm winter air was not sufficient to melt the layer of snow covering the sea ice, let alone the ice itself," Nicolaus said.
During the past winter, the growth of the arctic sea ice was significantly slower than the scientists had expected.
In previously ice-rich areas such as the Beaufort Gyre off the Alaskan coast or the region south of Spitsbergen, the sea ice is considerably thinner now than it normally is during the spring, researchers said.
"While the landfast ice north of Alaska usually has a thickness of 1.5 metres, our US colleagues are currently reporting measurements of less than one metre. Such thin ice will not survive the summer sun for long," said Stefan Hendricks, AWI sea ice physicist.