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Glaciers, Much More Dangerous Than Polar Ice SheetsThey dump twice more ice into the oceans |
By Stefan Anitei, Science Editor
9th of January 2007, 09:06 GMT
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When it's about global warming and ice melting, our attention is caught by Greenland and Antarctic ice sheets.
But scientists at University of Colorado at Boulder warn that small glaciers and ice caps are more to be taken in consideration as contributors to sea level rising. "More than half of the estimated 650 billion tons of ice lost to the oceans annually comes from the discharge of small glaciers and icecaps", said Professor Tad Pfeffer of CU-Boulder's Institute of Arctic and Alpine Research.
Glaciers are thought to be shedding 400 billion tons of ice (about the volume of Lake Erie) while Greenland and Antarctic combined ice sheets are estimated at 250 billion tons annually.
Sea level is rising at about 3 mm annually and could rise by several feet or more till the end of
the century at the current level of greenhouse gases emitted. "The message from our study is that small glaciers and ice caps are the biggest sources of water in global sea rise, which runs contrary to many news reports focusing on Antarctica and Greenland," said Pfeffer, a professor in the civil, environmental and architectural engineering department. "We feel that ignoring the contributions of small glaciers and icecaps is dangerous because it affects the accuracy of predictions of sea rise around the world."
There are several hundred thousand small glaciers and ice caps spread around the world, mostly in polar and temperate regions. Some can be huge, like the Bering Glacier in Alaska, the biggest glacier in continental North America, which measures about 5,000 square miles (13,000 square km) and in some places is nearly one-half mile thick. "Because of the challenge in inventorying each individual glacier, the researchers used a mathematical "scaling" process to estimate and characterize more remote glacier volumes, thicknesses and trends by factoring in data like altitude, climate and geography", said Emeritus Professor Mark Meier.
The research used data from around the world, from Russia, Northern Europe, China, to India, Nepal and South America. A 2005 study by the same team revealed that the Columbia Glacier (one of the 51 Alaskan glaciers that empty into the ocean and the largest glacial contributor to the sea level in North America) had shortened by 9 miles (15 km) since 1980 and was shedding two cubic miles (4 cubic km) of ice into Prince William Sound yearly. "We expect that small glaciers will be the biggest contributors to global sea rise for the next 50 to 100 years," said Meier. "Continued warming temperatures will likely cause most of the glaciers in the Rocky Mountains and Alps, for example, to disappear by the end of the century," Meier said.
"I don't think we can afford to wait until there is two feet of water in our livings rooms to start thinking about a response to changing climate," said Pfeffer.
"In addition to sea rise contributions, increasingly large discharges of fresh water into the oceans from glaciers and ice caps also may be having ecological impacts in coastal regions, including coastal Alaska," Pfeffer said.
Changes in ocean salinity and temperature alter the environment and the food chains for marine species.
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