Ice melt alert

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 sheet to melt, global sea levels could rise by a startling 23 feet, inundating most of the world's coastal cities.

The Himalayan Mountains contain the world's third largest ice mass after Antarctica and Greenland. Most Himalayan glaciers have been thinning and retreating over the past 30 years, with losses accelerating to alarming levels in the past decade. On Mt. Everest, the glacier that ended at the historic base camp of Edmund Hillary and Tenzing Norgay, the first humans to reach the summit, has retreated three miles since their 1953 ascent. Glaciers in Bhutan are receding at an average rate of 30-40 meters a year. A similar situation is found in Nepal.

As the glaciers melt, they are filling glacial lakes, creating a flood risk. An international team of scientists has warned that, with current melt rates, at least 44 glacial lakes in the Himalayas could burst their banks in as little as five years. Glaciers themselves store vast quantities of water. More than half of the world's population relies on water that originates in mountains, coming from rainfall runoff or ice melt. In some areas, glaciers help sustain a constant water supply; in others, meltwater is a primary water source during the dry season. In the short term, accelerated melting means that more water feeds rivers. Yet, as glaciers disappear, dry season river flow declines.

The Himalayan glaciers feed the seven major rivers of Asia--the Ganges, Indus, Brahmaputra, Salween, Mekong, Yangtze, and Huang He--and thus contribute to the year-round water supply of a vast population. In India alone, some 500,000,000 people, including those in New Delhi and Calcutta, depend on glacier meltwater that feeds into the Ganges River system. Glaciers in Central Asia's Tien Shan Mountains shrunk by nearly 30% between 1955-90. In arid western China, shrinking glaciers account for at least 10% of freshwater supplies.

The largest aggregation of tropical glaciers is in the northern Andes Mountains. The retreat of the Qori Kalis Glacier on the west side of the Quelccaya Ice Cap that stretches across Peru accelerated to 155 meters a year between 1998-2000-three times faster than during the previous three-year period. The en tire ice cap could vanish over the next two decades.

The Antizana Glacier, which provides Quito, Ecuador, with almost half its water, has retreated more than 90 meters over the last eight years. The Chacaltaya Glacier near La Paz, Bolivia, melted to seven percent of its 1940s volume by 1998. It could disappear entirely by the end of this decade, depriving the 1,500,000 people in La Paz and the nearby city of Alto of an important source of water and power.

Boundaries around Banff, Yoho, and Jasper National Parks in the Canadian Rockies cannot stop the melting of the glaciers there. Glacier National Park in Montana has lost over two-thirds of its glaciers. If temperatures continue to rise, it may lose the remainder by 2030.

In just the past 30 years, the average temperature in Alaska climbed more than 5[degrees]--easily four times the global rate. Glaciers in all of Alaska's 11 glaciated mountain ranges are shrinking. Since the mid 1990s, Alaskan glaciers have been thinning by 1.8 meters a year, more than three times as fast as during the preceding 40 years.

The average global temperature has climbed by 1[degrees] in the past 25 years. Over this time period, melting of sea ice and mountain glaciers has increased dramatically. During this century, global temperature may rise between 2.5-10.4 [degrees], and melting will accelerate further. Just how much will depend in part on the energy policy choices made today.

Janet Larsen is a research associate at Earth Policy Institute, Washington, D. C.

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