The Coastal Post - November 1999

Arctic Ice Cap Is Seriously Shrinking

By Jim Scanlon

A study funded by the National Science Foundation, the Office of Naval Research and NASA, set to appear December 1 in Geophysical Research Letters shows a "striking" decline in Arctic sea ice since the 1960s

Using data acquired by U.S. Navy submarines they report a "striking" reduction in the thickness of the Polar Ice Cap, as compared with 20 to 40 years ago. The average draft of the sea ice (that is, its thickness from the ocean surface to the bottom of the ice pack) has declined by 4.3 feet This represents a reduction of about 40 percent as compared with the earlier period.

The decrease occurs all across the arctic. The data was acquired on six extended cruises by nuclear submarines. The recent data coming from three cruises: by USS Pargo in 1993, USS Pogy in 1996, and USS Archerfish in 1997.

The recent data showed a perennial ice cover of from three to nine feet in mean draft, which was considerably thinner than previous estimates. The earlier data, used for comparison, began with the first nuclear submarine, USS Nautilus in 1958 and continued through a cruise of HMS Sovereign in 1976.

The changes are "striking in the uniformity of their sign and...magnitudes." That is, every one of the 29 sites showed a decline in ice thickness. This is not an instance of ice thinning in one area while thickening in another, which could be induced by a change in surface wind patterns.

The available data are reported insufficient to provide answers about the cause of the ice loss. A key topic for future research is whether ice volume has reached a minimum or whether the decline will continue into the future. Regardless, the thinning that has already occurred is "a major climatic signal that needs to be accounted for."

Earth Scientists usually refer to periods of 10,000 years of so as "extremely rapid change" so a change of 20-40% in such a vast area that has been in existence for millions of years is indeed extremely. The disappearance of the ice cap would result in climate change that can not be predicted, let alone imagined.

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