Published on Thursday, December 16, 2004 by Inter Press Service
Sea Levels to Rise Faster - NASA
by Stephen Leahy
BROOKLIN, CANADA -- The predicted rise in sea levels caused by the world's changing climate will have to be revised upward after U.S. scientists recorded accelerated melting of ice in the Arctic and Antarctic, one researcher said this week.
New and updated satellite data from Greenland, the Canadian Arctic and Antarctica show parts of these regions are rapidly melting and contributing three times as much than previously believed to sea level rise.
"This is the first time researchers have been able to get real data on this," said Waleed Abdalati, a researcher at the Goddard Space Flight Centre of the U.S National Aeronautics and Space Administration (NASA).
Abdalati and NASA colleagues presented their findings at a meeting of the American Geophysical Union in San Francisco this week.
The melting appears to be in direct response to the surface air temperature warming in these regions. What is alarming is how quickly these massive ice sheets are responding to temperature increases of around 2C, said the scientists.
"We're seeing a response in months rather than in centuries as previously believed," Abdalati told IPS.
About 10 percent of Earth's land is covered with glaciers, which store about 75 percent of the world's fresh water. If all land ice melted, sea level would rise approximately 70 m worldwide, according to the U.S. National Oceanographic and Atmospheric Administration (NOAA).
Greenland's largest glacier, the Jakobshavn Isbrae, is galloping towards the sea after about 50 years of doing very little, said Abdalati.
The ice mass began its charge seaward in the early 1990s in response to warmer air temperatures. By the mid-1990s it was the world's fastest glacier, moving at an unglacial clip of seven km a year. By 1997 it began to accelerate, and NASA says today it travels 13 km a year, dumping enormous amounts of ice into the sea.
In 2003 alone the Jakobshavn Isbrae contributed about four percent of the estimated rate of sea level rise worldwide, according to the agency.
Abdalati calls the speed of the meltdown "phenomenal" and says it suggests glaciers are not as stable as once thought.
Canadian and Alaskan glaciers are undergoing similar transformations, which began in the late 1990s and appear to be accelerating as well.
In 2001 the Intergovernmental Panel on Climate Change (IPCC) estimated global sea level would rise 0.4 m to 1 m by 2100. That estimate will have to be revised upward based on these findings says Abdalati.
The picture is more complex in the Antarctic, where parts of the frozen continent -- which holds nearly two-thirds of the planet's fresh water -- have gotten cooler, while the west Antarctic is warming.
NASA scientists reported this fall that a number of massive glaciers in the west are sliding into the ocean at accelerating rates and raising sea levels faster than expected.
"If the warming trend reaches other parts of the Antarctic we could see some major and rapid changes in the ice," said Ted Scambos of the University of Colorado's National Snow and Ice Data Centre.
"There could be changes in the sea levels happening more quickly than were thought possible," he added in a press conference.
Several large glaciers are currently bottled up by the Ross Ice Shelf, the main outlet for the West Antarctic Ice Sheet. Should the shelf break up as the Larsen B did in 2002, those glaciers would slide into the sea. Water levels could rise by 4 m if they melted completely.
The Arctic's perennial sea ice is also in decline. While this floating ice, which lasts year-long, does not contribute to sea level rise, any reduction in its coverage area allows more heat from the sun to be absorbed by the Arctic Ocean. That leads to more sea ice loss, which in turn means more open ocean for the sun to warm.
"It's the most remarkable change that has been observed in the Arctic thus far," said Josefino Comiso of NASA's GSFC.
Comiso now measures this ice cover decline at 9.2 percent per decade, up from a previous figure of 8.9 percent per decade in 2000.
Once again the change corresponds to warmer air temperatures observed over the past 20 years in much of the Arctic.
And the trend means an ice-free shipping route through the region via the Northwest Passage is not that far off, according to Comiso. "It's close to that right now."
Shipping via the passage from Europe to the Far East rather than using the current route through the Panama Canal would cut 4,000 km from the voyage.
However, the route would traverse a region Canada has long claimed as its own territory. The United States does not recognise that claim and has sent its own ships to explore the region. Months ago, Canada held its largest military exercise in the region - notably without U.S. military participants and observers.
And just a couple of months ago the first scientific evidence emerged hinting at the possibility of extensive oil and gas deposits in the Arctic Ocean.
Computer projections show Arctic warming will continue and the region will be 6C warmer on average by the end of this century, even if Kyoto Protocol commitments to cut the greenhouse gases -- such as carbon dioxide -- that cause global warming go into effect globally.
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