Ice melt alert.

• Author: Larsen, Janet
• Position: EYE ON ECOLOGY - Glaciers and sea ice respond to global warming

BY 2020, THE SNOWS OF MT. KILIMANJARO may exist only in old photographs. The glaciers in Montana's Glacier National Park could disappear by 2030. Come mid century, the Arctic Sea may be completely ice-free during summertime. As the Earth's temperature has risen in recent decades, its ice cover has begun to melt--and that melting is accelerating.

In 2002-03, the Northern Hemisphere registered record-low sea ice cover. New satellite data show the Arctic region warming more during the 1990s than during the 1980s, with Arctic Sea ice now melting by up to 15% per decade. The long-sought Northwest Passage, a dream of early explorers, could become our nightmare. The loss of Arctic Sea ice could alter ocean circulation patterns and trigger changes in climate patterns worldwide.

On the opposite end of the globe, Southern Ocean sea ice floating near Antarctica has shrunk by some 20% since 1950. This unprecedented melting corroborates records showing that the regional air temperature has increased by 4.5[degrees]F since 1950. Antarctic ice shelves that have existed for thousands of years are crumbling. One of the world's largest icebergs, named B-15, that measured nearly 4,000 square miles, or half the size of New Jersey, calved off the Ross Ice Shelf in March, 2000. In May, 2002, the shelf lost another section, measuring 19 miles wide by 124 miles long. Elsewhere on Antarctica, the Larsen Ice Shelf has disintegrated to 40% of its previously stable size in the last decade. Following the break-off of the Larsen A section in 1995 and the collapse of Larsen B in 2002, melting of the nearby land-based glaciers has more than doubled.

Unlike the melting of sea ice or the floating ice shelves along coasts, the melting of ice on land raises sea level. Recent studies showing the worldwide acceleration of glacier melting indicate that the Intergovernmental Panel on Climate Change's estimate for sea level rise this century--ranging from 0.1 meters to 0.9 meters--will need to be revised upwards.

On Greenland, an ice-covered island three times the size of Texas, once-stable glaciers are melting at a quickening pace. The Jakobshavn Glacier on the island's southwest coast, which is one of the major drainage outlets from the interior ice sheet, currently is thinning four times faster than during most of the 20th century. Each year, Greenland loses some 51 cubic kilometers of ice, enough to raise the sea level 0.13 millimeters annually. Were Greenland's entire ice...