The Age of Icelessness

By Danielle Murray, Environment News Service. Posted February 25, 2005.

Ice is melting everywhere – and at an accelerating rate. Rising global temperatures are lengthening melting seasons, thawing frozen ground, and thinning ice caps and glaciers that in some cases have existed for millennia. These changes are raising sea level faster than earlier projected by scientists, and threatening both human and wildlife populations.

Since the industrial revolution, human activity has released ever-increasing amounts of carbon dioxide and other greenhouses gases into the atmosphere, leading to gradual but unmistakable changes in climate throughout the world – especially at the higher latitudes.

Average surface temperatures in the Arctic Circle have risen by more than half a degree Celsius (0.9 degrees Fahrenheit) per decade since 1981. The extent of Arctic sea ice cover has decreased by 7-9 percent per decade. And the three smallest extents of summer ice ever seen there have all occurred since 2002. According to the latest forecasts, the Arctic could be ice-free in the summer by the end of this century.

The Arctic melt season has lengthened by 10-17 days, shrinking the amount of ice buildup that remains from year to year. As sea ice thins and recedes from coastlines, indigenous hunters and fishers are finding themselves cut off from traditional hunting grounds. Coastal communities face more violent and less predictable weather, rising sea levels, and diminishing access to food sources. Polar bears, unable to cross thin or nonexistent ice to hunt seals, will soon face a severely reduced food source.

Scientists fear that with continued melting, the bears may become extinct by the end of the century. Seals, walruses, and seabirds will also lose key feeding and breeding grounds along the ice edge.

Marine transport through the Arctic is expected to increase as ice melts and new shipping routes become available. The length of the navigation season along the Northern Sea Route is projected to increase to about 120 days by 2100, up from the current 20-30 days. While this could have positive economic effects, some observers worry about the environmental costs that might accompany increased ship access to Arctic waters, such as oil spills and fishery depletion.

Arctic permafrost has warmed by up to 2 degrees Celsius in recent decades, with soils thawing to greater depths. By the end of this century, the southern permafrost boundary is projected to shift northward by several hundred kilometers, changing regional vegetation patterns.

An estimated 15 percent of the Arctic tundra has already been lost since the 1970s – an area roughly three times the size of California. As permafrost thaws, unstable ground shifts or subsides, damaging buildings, roads, pipelines, and other infrastructure in areas such as Alaska and Siberia.

The Greenland ice sheet is the largest land ice mass in the Northern Hemisphere. It holds enough fresh water to raise the earth's sea level by 7.2 meters (24 feet) if it were to melt completely, a result expected if the regional temperature rises 3 degrees Celsius. Scientists project that concentrations of greenhouse gases will be high enough by 2100 to push temperatures past this threshold. Satellite data show Greenland's ice has been melting at higher and higher elevations every year since 1979.

A conservative estimate of annual ice loss from Greenland is 50 cubic kilometers (12 cubic miles) per year, enough water to raise the global sea level by 0.13 millimeters a year.

The Amundsen Sea region in the West Antarctic has experienced some of the world's greatest temperature change, with annual temperatures up 2.5 degrees Celsius over the past 60 years. The glaciers flowing into the sea from the Antarctic continent have been getting thinner for the past 15 years, and ice shelves in the region have decreased by more than 13,500 square kilometers since the 1970s.

Since the collapse of the Delaware-sized Larsen B Ice Shelf in 2002, satellites have shown a two-to-sixfold increase in the speed of glaciers flowing toward the former ice shelf. While most glaciers typically move a few centimeters to several hundred meters annually, these glaciers are currently moving as much as 1.5 kilometers each year.

This type of acceleration has been witnessed throughout Antarctica and Greenland when ice shelves collapse, removing the barrier to the sea for interior glaciers and quickening the rate of fresh water loss to the ocean.

Glaciers in West Antarctica are discharging about 250 cubic kilometers of ice and water into the ocean per year, 60 percent more than is accumulated in their catchment areas – a net change sufficient to raise global sea levels by more than 0.2 millimeters per year.

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