Nov 19 2009
A new study of Antarctica's climate history shows that in some brief warm periods between ice ages, temperatures were up to 6°C warmer than the present day. The findings, reported this week in the journal Nature, could help us understand more about rapid climate changes.
Scientists from the British Antarctic Survey (BAS), the Open University and the University of Bristol, explain that until now temperatures during the warm periods between ice ages - known as interglacials - were thought to be slightly warmer than those of the present day. However, some brief 'spikes' in temperature, which recur roughly every 100 000 years and last a few thousand years seem to have been a lot warmer.
Lead author, Louise Sime from BAS, said: "We analysed Antarctic ice cores to look at climate during past warm periods and were surprised to find relatively high Antarctic temperatures during some spikes. We don't yet know what caused these peaks, but we would like to be sure we haven't missed anything important about how Antarctica is set to change in a warming world."
Julia Tindall, an author of the paper from the University of Bristol, added: "It is quite difficult to reconstruct temperatures from long ago. Although it is generally accepted that the climate was warmer 125,000 years ago, our results suggests it was much warmer than previously thought. It will be interesting to see if other studies agree with our findings".
Ice cores from East Antarctica contain the oldest drilled ice on Earth, and provide a unique record of past climate. Analysis of the ice cores has revolutionized our understanding of how Antarctic climate has varied in the past.
Ice core scientist Eric Wolff of British Antarctic Survey is a world-leading expert on past climate. He said: "During the last warm period, about 125 000 years ago, sea level was around 5 metres higher than today. If we can pin down how much warmer temperatures were in Antarctica and Greenland at this time, then we can test predictions of how melting of the large ice sheets will contribute to sea level rise."
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Further information:
The paper: Evidence for warmer interglacials in East Antarctic ice cores by Louise C. Sime, Eric W. Wolff, Kevin I. C. Oliver and Julia C. Tindall is published online this week in Nature.
Direct sea level measurements based upon coastal sedimentary deposits and tropical coral sequences have established that global sea level was higher than present during the last interglacial (~125 000 years ago) by approximately 4 to 6 m. This indicates that the Greenland and Antarctic ice-sheets were smaller than during the present day.
Ice cores are unique climate records, allowing scientists to investigate climate changes over hundreds of thousands of years. The Earth's oldest ice is found in the Antarctic. The three oldest existing ice cores were drilled at Dome C, Dome F and Vostock. The longest ice core - at 3,650 metres - comes from Vostock, but the oldest ice core, drilled by the European Project for Ice Coring in Antarctica (EPICA) team, contains a climate record stretching back 800,000 years. Information from ice cores is vital for testing and improving the computer models used to predict future climate.
This research was funded by the Natural Environment Research Council.