Talk by Dorthe Dahl-Jensen, CIC

Title:  Present day Greenland Ice Sheet replaced boreal forest more than 900 Thousand Years ago.

Abstract: Knowledge on the Greenland ice sheet’s long-term response to warming during earlier interglacials is crucial to estimate future sea level rise. Through environmental DNA from basal ice from the Camp Century ice core in Northwestern Greenland we show that this area was covered by mixed deciduous and conifer forests at the time of formation of the present Greenland Ice Sheet.

The findings require at least 10^oC warmer temperatures than at present, similar to the temperature increase needed to support the Kap København conifer forest 2-2.5 Ma BP. We date the event of ice covering the Camp Century vegetation to 0.5 to 2.4 million years BP (Ma). By coupling our findings to dates and DNA of the GRIP (>0.9 Ma) and the Dye3 (>0.5 Ma) basal ice from central and southern Greenland we conclude that the main Greenland ice sheet must have settled quickly between 0.9 and 2.4 Ma in a Greenland that was largely covered by forest. The findings imply that substantial warming is required to deglaciate Greenland and improves and constrains estimates of future sea level rise.