A glimpse into the Eemian
Ice from the last interglacial, the Eemian, has been found near the bedrock in all deep ice cores retrieved from the Greenland ice sheet, but only in the NGRIP ice core is the Eemian ice undisturbed. At the GRIP drill site, Glacial ice has been folded into the ice from the Eemian period by complex ice flow. At DYE-3, ice flow over mountainous bedrock starts to obscure the δ18O record in ice only 40,000 years old. Dansgaard-Oeschger events 24 and 25 cannot be found in the Camp Century and Renland δ18O records, casting serious doubt on the integrity of the older Eemian ice layers in these cores. Hence, at present the NGRIP ice core is the only core from Greenland that shows Dansgaard-Oeschger events 24 and 25 as well as some of the Eemian warm period.
A new Eemian record
A new deep drilling north-west of NGRIP (the NEEM project) has as its main goal to retrieve undisturbed ice from the entire Eemian period. The NEEM deep drilling will be carried out from 2008 to 2011, but initial investigations at the NEEM site have already commenced in the summer of 2007.
Previous climate warmth
So far the ice cores can only provide us a glimpse into the Eemian warm period. But we can already tell that Eemian climate was significantly warmer than the climate of the current Holocene interglacial - probably about 5°C warmer. As ice from the Eemian period (albeit disturbed) has been found at all drill sites, we also know that the Greenland ice sheet did not melt away entirely during the warmth of the Eemian. Close analysis of δ18O values in the Eemian ice does indeed suggest that the Eemian Greenland ice sheet was not dramatically smaller than today.
Ice Core Drilling Projects
For more information on the topic please contact Bo Vinther