UN Navy data shows Arctic Sea ice has reduced by 40% in less than 40 years

A study to be published in the 1 December issue of Geophysical Research Letters shows that the average thickness of the sea ice has declined by 1.3 metres, or 40%, from the 1960s. In certain areas, such as the Nansen Basin and the eastern Arctic, the thinning is as high as 1.7 metres.

The researchers have noted that the uniformity of the reductions – there is no pattern of ice thinning in one area but thickening in another – rules out the influence of changing surface wind patterns. As to the cause of the thinning, several hypotheses are put forward:

• flow of heat from the ocean
• flow of heat from the atmosphere
• shortwave radiation

Whatever the specific cause, the researchers believe that it constitutes “a major climatic signal that needs to be accounted for in a successful theory of climate variability”.

The thinning of the Arctic Sea ice involved data taken from three autumn cruises by US Navy nuclear submarines in 1993, 1996 and 1997 and comparisons with similar data taken in the 1960s and early 1970s. The researchers note that very little information is available from the 1976 to 1993 period, and that the public release of ice thickness data from this period would be “of immense help”.