Ice age studies reveal further concern over Greenland ice sheet

by Rich Bowden - Aug 31 2008, 21:37

Estimates of sea level rise due to the melting of the Greenland ice sheet will need to be revised upwards according to researchers who have studied the rapid meltdown of the last North American ice sheet.

An international team of scientists, led by the University of Wisconsin, used analysis of the Laurentide ice sheet, which melted from North America around 6,500 years ago, and found the expected sea level rise as a result of the meltdown may be two or three times higher than currently estimated.

"We have never seen an ice sheet retreat significantly or even disappear before, yet this may happen for the Greenland Ice Sheet in the coming centuries to millennia," said Anders Carlson, the study's lead author and assistant professor of geology and geophysics at the University of Wisconsin-Madison.

"What we don't know is the rate of melting of the Greenland Ice Sheet. The geologic data we compiled on the retreat history of the Laurentide Ice Sheet, however, gives us a window into how fast these large blocks of ice can melt and raise sea level."

Estimates in 2007 by the Intergovernmental Panel on Climate Change (IPCC) predicted oceans would rise by 18 and 59 centimetres (7.2 and 23.2 inches) by 2100. However the Panel later said more information about the role meltwater from the Antarctic and Greenland was needed for a more accurate assessment.

"We're not talking about something catastrophic, but 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 Carlson, who was joined in the study by an international team including Allegra LeGrande from the NASA Centre for Climate Systems at Columbia University, and colleagues at the Woods Hole Oceanographic Institution, the California Institute of Technology, University of British Columbia and University of New Hampshire.

Scientists have debated exactly what effect the melting of the Greenland ice sheet will have on global sea levels and part of the disagreement has been that data has been unavailable on the influence of climate change on the melting of ice sheets.

"We've never seen an ice sheet disappear before, but here we have a record," said Carlson in the research, which is published in the journal Nature Geoscience.

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