On entering an era of global warming, the stability of the Greenland ice sheet (GIS) is an important concern1, especially in the light of new evidence of rapidly changing flow and melt conditions at the GIS margins2. Studying the response of the GIS to past climatic change may help to advance our understanding of GIS dynamics. The previous interpretation of evidence from stable isotopes (δ18O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially3 and that a consistent Holocene climate optimum-the unusually warm period from about 9,000 to 6,000 years ago found in many northern-latitude palaeoclimate records4-did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing delta O-18 from GIS ice cores(3,5) with δ18O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of δ18O evidence from ice cores3,6, our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our δ18O-based results are corroborated by the air content of ice cores, a proxy for surface elevation7. State-of-the-art ice sheet models are generally found to be underestimating the extent and changes in GIS elevation and area; our findings may help to improve the ability of models to reproduce the GIS response to Holocene climate.
|Number of pages||4|
|Publication status||Published - 2009|