The central Greenland ice cores
In 1989 the very summit of the Greenland ice sheet was selected as the site for the next deep drilling, and by the summer of 1992 a 3029 m deep ice core reaching all the way to bedrock had been retrieved using the ISTUK drill as part of the mainly European GReenland Ice core Project (GRIP). In 1993 an American team reached bedrock 30 km west of the GRIP drill site as part of the GISP2 project (Meese et al. (1997)).
While both the Camp Century and DYE-3 ice cores contained only a few hundred of meters of glacial ice, the glacial sections comprised about half of the more than 3 km long GRIP and GISP2 ice cores. Combining this much-improved resolution with large advances in ice core analysis techniques, the Central Greenland ice cores advanced the knowledge about glacial climate enormously. However, comparisons of the two ice cores made it clear that although both cores provide excellent records of past climatic conditions some 105,000 years back in time, the stratigraphies of the bottom ~300 m of both cores are disturbed. The ice has been flowing over the uneven bedrock topography in the area which has resulted in folding of the layers older than 105,000 years. This means that the ice deposited during the Eemian warm period some 115,000 - 130,000 years ago is disturbed.
Ice Core Drilling Projects