Updated:
Original:

Break in ice shelf called early warning of climate warming trend

The largest remnant of an ice shelf that rimmed Ellesmere Island in the Canadian Arctic a century ago has cracked in two, said researchers in a forthcoming issue of Geophysical Research Letters.

According to Washington Post interviews with the scientists and a preview of their article, the Ward Hunt Ice Shelf developed a fissure in 2000. The original fissure has widened since and others have appeared, renewing a century-long meltdown and breakup of the ice shelf that had appeared to stabilize in 1982, with approximately 90 percent of the shelf already gone. The recent fissures have drained a freshwater lake the shelf had dammed beneath the surface ice of Disraeli Fjord.

A dramatic rise in average temperatures in the Canadian Arctic since 1967 has led to puddling on the ice sheet. The puddles, darker in coloration than the ice, absorb heat better and accelerate melting, the Post reports.

The scientists interviewed by the Post said human activity - the complex of gaseous releases and their "greenhouse effect" in the atmosphere, known as global warming - probably cannot alone explain the evidence of Arctic-wide warming in recent years. Those dramatic changes must be linked to prolonged worldwide climate patterns, they told the Post.

Geophysicist Martin O. Jeffries, University of Alaska at Fairbanks, said the findings in the Canadian Arctic are consistent with the larger pattern. He noted the widely accepted view that climate warming would affect the polar regions first, and added "This could be part of that signal." Ralph J. Cicerone, an atmospheric chemist at the University of California at Irvine, told the Post the melting ice and permafrost thaw "is a good dress rehearsal" for future decades.