Doctoral Dissertation Research: A Comparison of the Holocene Extents of the Greenland Ice Sheet in Western and Eastern Greenland

Dartmouth College, Hanover NH

Investigators

Abstract

The Arctic is currently warming more rapidly than other locations on the planet and the response of the Greenland Ice Sheet to this warming is a focus of many current studies. Model projections of the contribution of the Greenland Ice Sheet to global sea level rise range from 4.5 to 17 cm by 2100. This project will help to understand the possible response of the Greenland Ice Sheet to future warming by developing records of the ice sheet margin during past warm times particularly during recent interglacial period (the Holocene Epoch, 11,650 years B.P. to present). The research will focus on the Kangerlussuaq region (67.0N, 50.7W) in western Greenland where a record of ice margin extents during the Holocene is marked by belts of prominent, well-preserved moraine ridges. Preliminary ages of moraines, determined by surface-exposure dating using the cosmogenic nuclide Beryllium-10, demonstrate the ability to date precisely the moraines near Kangerlussuaq. Results from one set of moraines, the ?Orkendalen moraines?, located just outboard of (and in some places adjacent to) the historical moraines, indicate that the Greenland Ice Sheet was smaller than at present between ~6,500 years ago and the historical advance culminating in A.D. 1850. The project will develop a chronology of the Greenland Ice Sheet margin fluctuations near Kangerlussuaq using a combination of detailed geomorphic mapping and surface-exposure dating of moraines. Ice sheet margin fluctuations will be compared with Holocene records of insolation, ocean circulation and surface air temperatures to examine the possible climate mechanisms that may have influenced the fluctuations of Holocene ice extent in eastern Greenland. The timing and spatial continuity of these fluctuations will provide insight into how the Greenland Ice Sheet will respond to future climate changes. This research will produce the first directly dated ice margin chronology in the Kangerlussuaq region in Greenland. Ice cores from the Greenland Ice Sheet register temperature, dustiness and other atmospheric conditions over the ice sheet, but do not provide information on how the sensitive margins of the ice sheet have changed. Combined with data from eastern Greenland, this new record from western Greenland will provide a geographically broad, spatial comparison of ice margin fluctuations that will be useful for testing hypotheses of climate mechanisms that cause ice sheet variability. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.