The aim of this collaborative project between investigators at three universities is to develop records of past climate in northwest (NW) Greenland and synthesize them with records of the position of ice margin to evaluate the response of the Greenland Ice Sheet to past warm periods, such as the Holocene Climatic Optimum (approximately 5 to 9 thousand years ago). Recent studies suggest that rapid ice loss is expanding northwards into NW Greenland, as demonstrated by the dramatic August, 2010 calving event from Petermann Glacier. However, little paleoclimate and ice sheet research has been conducted in NW Greenland, despite the proximity to a logistics center at Thule Air Base. The proposed research integrates multiple climate proxies and glaciological modeling experiments in the Thule region with the following research objectives: 1) Reconstruct Holocene climate in NW Greenland via inferences from reconstructed local ice cap extents (North Ice Cap, Tuto Ice Cap), ice core stable isotope and precipitation records, and data from nearby lake sediments. 2) Examine the sensitivity of the NW Greenland Ice Sheet (GIS) to Holocene climate changes by developing the history of the areal extent of the GIS and synthesizing proxy data with glaciological modeling experiments to examine past GIS changes and predict future GIS retreat. Results from the proposed research will enable a more accurate prediction of the NW Greenland cryospheric response to a future warmer world and provide information directly relevant to predictions of future sea-Âlevel rise. The investigators propose to enhance public outreach and K-Â12 science education through development of educational modules using simplified, web-Âbased, climate and glaciological models. They would involve graduate and undergraduate students in field and lab research, participate in the Dartmouth WomenÂ In Science Project, and partner with the Dartmouth polar IGERT program.