Researchers used new data from the European Space Agency's CryoSat-2 satellite spanning 2010 to 2012, and data from NASA's ICESat satellite from 2003 to 2008 to estimate sea ice volume in the Arctic. They found that from 2003 to 2008, autumn volumes of ice averaged 11,900 cubic kilometres. But from 2010 to 2012, the average volume fell to 7600 cubic kilometers – a decline of 4300. Average winter ice volume from 2003 to 2008 was 16,300 cubic kilometers, dropping to 14,800 cubic kilometers between 2010 and 2012 – a difference of 1500.
Researchers published the study online in Geophysical Research Letters. "Other people had argued that 75 to 80 percent ice volume loss was too aggressive," said co-author Axel Schweiger in a press release. "What this new paper shows is that our ice loss estimates may have been too conservative, and that the recent decline is possibly more rapid."
Dr. Katharine Giles, from the Centre for Polar Observation and Modelling (CPOM) at University College London explains further. "Thin ice grows more quickly than thick ice in the winter. Ice acts as an insulator - the thinner the ice, the more heat can be lost to the atmosphere and the faster the water beneath the ice can freeze," Dr. Giles told BBC News. "But even with an increased ice growth during the winter, we can see from the Cryosat data that it's still not fully compensating for the deep summer melt."
As the sea ice melts — and researchers expect to see ice-free summers in coming years — it opens the Arctic to increased oil exploration and shipping channels. For the first time, a "Northwest Passage" might be available to border nations for commerce on a regular basis.