Ice Age lesson foretells faster rise in sea level

September 1st, 2008 - 3:23 pm ICT by IANS  

Washington, Sep 1 (IANS) A rise in sea level from greenhouse-induced warming of the Greenland ice sheet could be double or triple of current estimates over the next century, warned a team of researchers. “We could see a much bigger response in terms of sea level from the Greenland ice sheet over the next 100 years than what is currently predicted,” said Anders Carlson, University of Wisconsin (UW) Madison professor of geology and geophysics, who led the research team.

Carlson worked with an international team of researchers, including Allegra LeGrande from the NASA Centre for Climate Systems at Columbia University, and colleagues at the Woods Hole Oceanographic Institution, California Institute of Technology, University of British Columbia and University of New Hampshire.

Scientists have yet to agree on how much melting of the Greenland ice sheet -encompassing 1.7 million square km - will contribute to changes in sea level.

One reason, Carlson explained, is that in recorded history there is no precedent for the influence of climate change on a massive ice sheet.

“We’ve never seen an ice sheet disappear before, but here we have a record,” said Carlson of the new study that combined a powerful computer model with marine and terrestrial records to provide a snapshot of how fast ice sheets can melt and raise sea level in a warmer world.

Carlson and his group were able to draw on the lessons of the disappearance of the Laurentide ice sheet, the last great ice mass to cover much of the northern hemisphere.

The Laurentide ice sheet, which encompassed large parts of what are now Canada and the US, began to melt about 10,000 years ago in response to increased solar radiation in the northern hemisphere due to a cyclic change in the orientation of the Earth’s axis.

Those pulses of melting, according to the new study, occurred when summer air temperatures were similar to what are predicted for Greenland by the end of this century.

The most recent estimates of sea level rise due to melting of the Greenland ice sheet by the Intergovernmental Panel on Climate Change (IPCC) suggest a maximum sea level rise during the next 100 years of about one to four inches.

That estimate, Carlson and his colleagues note, is based on limited data, mostly from the last decade, and contrasts sharply with results from computer models of future climate, casting doubt on current estimates of change in sea level due to melting ice sheets.

Even slight rises in global sea level are problematic as a significant percentage of the global population - hundreds of millions of people - lives in areas that can be affected by rising seas.

These findings were published in the Sunday edition of Nature Geoscience.

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