Study: Melting Antarctic Glacier Raising Sea Level
WASHINGTON (Reuters) - A huge but remote Antarctic glacier is thinning at rates fast enough to raise global sea levels, British researchers say.
The whole Pine Island Glacier, which is the largest glacier in West Antarctica, may be afloat in 600 years if it keeps thinning at the present rate, the team at University College London and the British Antarctic Survey said.
But while global warming often is blamed for such events, the researchers said Thursday that they do not know the cause just yet.
"We don't have any evidence to suggest change of climate," physicist Andrew Shepherd, who led the study, said in a telephone interview.
"This was not part of our research. This could be due to a variety of causes," he added.
Researchers say large chunks are breaking off of Antarctica for several reasons, some due to global warming.
For example, the West Antarctic Ice Sheet (WAIS) has been steadily melting since the end of the last ice age. But human-induced global warming can speed the process.
The WAIS contains enough ice to raise global sea levels by five to 18 feet if it melted.
Much of Antarctica consists of ice sheets with no ground underneath. If the ice melts it could not only raise ocean levels but could shift ocean circulation and weather patterns, bringing drought, severe storms and the wider spread of tropical diseases.
The Pine Island Glacier is the largest glacier in the WAIS.
Shepherd and colleagues used satellite measurements to check how thick the ice was and how quickly it was moving between 1992 and 1999.
GLACIER IS REMOTE
"This is a really remote area of Antarctica," Shepherd said. "There are no weather stations, no real-time data. All we can do is remotely sense what is happening."
It seems the glacier is flowing too quickly to sustain itself, spreading out thin and losing ice mass, he said.
In a report published in Friday's issue of the journal Science, the researchers estimate the mass of the glacier is decreasing by approximately 4 gigatons per year -- the equivalent of a rise in sea level of about .01 millimeters.
"Over the past eight years the same area has been thinning at the same rate. The pattern has not spread anywhere else," Shepherd said.
So, he and his colleagues have made very conservative predictions about what could happen.
"(Eventually) what would happen is the fast-flowing section of glacier would become afloat," Shepherd said. "It would be a large ice shelf and would contribute about 6 mm (a quarter of an inch) to global sea level, which isn't much ... I think the people in Florida are OK for now."
But Shepherd noted that the area is considered very unstable and many scientists believe that such a big change in one area inevitably would spread to others. "If that is the case, our estimates are wildly inaccurate," he said.
The United Nations-sponsored Intergovernmental Panel on Climate Change (IPCC) predicts the average global temperature could change by be as much as 11 degrees F higher at the end of the century than it was in 1990. If this affected the Antarctic, it could melt ice significantly and raise sea levels enough to swamp coastal areas.
Now the glacier rests on bedrock more than a mile below sea level. Half the glacier is above sea level and half below. Like all glaciers, it flows or moves steadily from inland to the sea.
Shepherd said all that can be done is to watch the ice sheet. "We have monitored the change for the first time and it is important for us now to continue to model it," he said.
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