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Ancient Greenland ice sheet growth linked to falling CO2 levels
New research by scientists from University of Bristol, British Antarctic Survey (BAS) and the University of Leeds reveals that a fall in levels of atmospheric carbon dioxide (CO2), close to that of pre-industrial times, explains the transition from a mostly ice-free Greenland of three million years ago to the ice-covered region we see today.
Reporting this week (27 August 2008) in the journal Nature the researchers describe how they used state-of-the-art computer climate and ice-sheet models to investigate the growth of Greenland’s ice sheet. They found that although the amount of ice cover was affected by changes in ocean circulation, increasing height of the Rocky Mountains, natural changes in greenhouse gases; and that the ice waxed and waned with changes in the Earth’s orbit, none of these changes were large enough to contribute significantly to the long-term growth of the Greenland ice sheet.
Dr Dan Lunt from the University of Bristol and BAS explained,
"We know from the geological record that the Greenland Ice Sheet has grown and retreated over time. Our study leads us to conclude that around three million years ago carbon dioxide levels fell to levels more similar to those recorded for pre-industrial times. From this point large amounts of ice began to transform the relatively ice-free landscape - which was probably covered in grass and forests - into the vast ice sheet that we see today. Of course, the million dollar question is why the elevated atmospheric carbon dioxide levels fell in the first place."
Today’s atmospheric CO2 levels are currently approaching that which existed while Greenland was mostly ice-free. Understanding why the ice formed on Greenland three million years ago will help understand the possible response of the ice sheet to current and future climate warming.
This work was carried out in the framework of the British Antarctic Survey Greenhouse to ice-house: Evolution of the Antarctic Cryosphere and Palaeoenvironment programme. Dan J.Lunt is funded by British Antarctic Survey and Research Councils UK fellowships. Gavin L. Foster is funded by a NERC research fellowship. Emma J Stone is funded by a NERC studentship.
Daniel J. Lunt, Gavin L. Foster, Alan M. Haywood, & Emma J. Stone
Nature, 28 August 2008, doi:10.1038/nature07223