By 2020, the snows of Kilimanjaro may exist only in old photographs. Theglaciers in Montana's Glacier National Park could disappear by 2030. And bymid-century, the Arctic Sea may be completely ice-free during summertime. Asthe earth's temperature has risen in recent decades, the earth's ice coverhas begun to melt. And that melting is accelerating.
In both 2002 and 2003, the Northern Hemisphere registered record-low sea icecover. New satellite data show the Arctic region warming more during the1990s than during the 1980s, with Arctic Sea ice now melting by up to 15percent per decade. The long-sought Northwest Passage, a dream of earlyexplorers, could become our nightmare. The loss of Arctic Sea ice couldalter ocean circulation patterns and trigger changes in global climatepatterns.
On the opposite end of the globe, Southern Ocean sea ice floating nearAntarctica has shrunk by some 20 percent since 1950. This unprecedentedmelting of sea ice corroborates records showing that the regional airtemperature has increased by 2.5 degrees Celsius (4.5 degrees Fahrenheit)since 1950.
Antarctic ice shelves that existed for thousands of years are crumbling. Oneof the world's largest icebergs, named B-15, that measured near 10,000square kilometers (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 lostanother section measuring 31 kilometers (19 miles) wide and 200 kilometers(124 miles) long.
Elsewhere on Antarctica, the Larsen Ice Shelf has largely disintegratedwithin the last decade, shrinking to 40 percent of its previously stablesize. Following the break-off of the Larsen A section in 1995 and thecollapse of Larsen B in early 2002, melting of the nearby land-basedglaciers that the ice shelves once supported has more than doubled.
Unlike the melting of sea ice or the floating ice shelves along coasts, themelting of ice on land raises sea level. Recent studies showing theworldwide acceleration of glacier melting indicate that theIntergovernmental Panel on Climate Change's estimate for sea level rise thiscentury--ranging from 0.1 meters to 0.9 meters--will need to be revisedupwards.
On Greenland, an ice-covered island three times the size of Texas,once-stable glaciers are now melting at a quickening rate. The JakobshavnGlacier on the island's southwest coast, which is one of the major drainageoutlets from the interior ice sheet, is now thinning four times faster thanduring most of the twentieth century. Each year Greenland loses some 51cubic kilometers of ice, enough to annually raise sea level 0.13millimeters. Were Greenland's entire ice sheet to melt, global sea levelcould rise by a startling 7 meters (23 feet), inundating most of the world'scoastal cities.
The Himalayas contain the world's third largest ice mass after Antarcticaand Greenland. Most Himalayan glaciers have been thinning and retreatingover the past 30 years, with losses accelerating to alarming levels in thepast decade. On Mount Everest, the glacier that ended at the historic basecamp of Edmund Hillary and Tenzing Norgay, the first humans to reach thesummit, has retreated 5 kilometers (3 miles) since their 1953 ascent.Glaciers in Bhutan are retreating at an average rate of 30-40 meters a year.A similar situation is found in Nepal.
As the glaciers melt they are rapidly filling glacial lakes, creating aflood risk. An international team of scientists has warned that with currentmelt rates, at least 44 glacial lakes in the Himalayas could burst theirbanks in as little as five years.
Glaciers themselves store vast quantities of water. More than half of theworld's population relies on water that originates in mountains, coming fromrainfall runoff or ice melt. In some areas glaciers help sustain a constantwater supply; in others, meltwater from glaciers is a primary water sourceduring the dry season. In the short term, accelerated melting means thatmore water feeds rivers. Yet as glaciers disappear, dry season river flowdeclines.
The Himalayan glaciers feed the seven major rivers of Asia--the Ganges,Indus, Brahmaputra, Salween, Mekong, Yangtze, and Huang He (Yellow)--andthus contribute to the year-round water supply of a vast population. InIndia alone, some 500 million people, including those in New Delhi andCalcutta, depend on glacier meltwater that feeds into the Ganges Riversystem. Glaciers in Central Asia's Tien Shan Mountains have shrunk by nearly 30 percent between 1955 and 1990. In arid western China, shrinking glaciers account for at least 10 percent of freshwater supplies.
The largest aggregation of tropical glaciers is in the northern Andes. Theretreat of the Qori Kalis Glacier on the west side of the Quelccaya Ice Capthat stretches across Peru has accelerated to 155 meters a year between 1998 and 2000-three times faster than during the previous three-year period. Theentire ice cap could vanish over the next two decades.
The Antizana Glacier, which provides Quito, Ecuador, with almost half itswater, has retreated more than 90 meters over the last eight years. TheChacaltaya Glacier near La Paz, Bolivia, melted to 7 percent of its 1940svolume by 1998. It could disappear entirely by the end of this decade,depriving the 1.5 million people in La Paz and the nearby city of Alto of animportant source of water and power.
Africa's glaciers are also disappearing. Across the continent, mountainglaciers have shrunk to one third their size over the twentieth century. OnKenya's Kilimanjaro, ice cover has shrunk by more than 33 percent since1989. By 2020 it could be completely gone.
In Western Europe, glacial area has shrunk by up to 40 percent and glacialvolume by more than half since 1850. If temperatures continue to rise atrecent rates, major sections of glaciers covering the Alps and the Frenchand Spanish Pyrenees could be gone in the next few decades. During therecord-high temperature summer of 2003, some Swiss glaciers retreated by anunprecedented 150 meters. The United Nations Environment Programme iswarning that for this region long associated with ice and snow, warmingtemperatures signify the demise of a popular ski industry, not to mention acultural identity.
Boundaries around Banff, Yoho, and Jasper National Parks in the Canadian Rockies cannot stop the melting of the glaciers there. Glacier National Parkin Montana has lost over two thirds of its glaciers since 1850. Iftemperatures continue to rise, it may lose the remainder by 2030.
In just the past 30 years, the average temperature in Alaska climbed more than 3 degrees Celsius (5 degrees Fahrenheit)-easily four times the global increase. Glaciers in all of Alaska's 11 glaciated mountain ranges areshrinking. Since the mid-1990s, Alaskan glaciers have been thinning by 1.8meters a year, more than three times as fast as during the preceding 40years.
The global average temperature has climbed by 0.6 degrees Celsius (1 degree Fahrenheit) in the past 25 years. Over this time period, melting of sea iceand mountain glaciers has increased dramatically. During this century,global temperature may rise between 1.4 and 5.8 degrees Celsius, and meltingwill accelerate further. Just how much will depend in part on the energypolicy choices made today.
Written by: Janet Larsen
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