AN EARLY HOLOCENE 10BE ALPINE GLACIER CHRONOLOGY AND PALEOCLIMATE RECONSTRUCTION FROM CENTRAL WEST GREENLAND

Much of the previous research conducted in Greenland has focused on the Greenland Ice Sheet (GrIS), in large part due to its potential impact on future sea level rise. Alpine glaciers, however, act as sensitive indicators of climate, and as such they may serve as the first responders to increasing global temperature. As we increase our understanding of GrIS margin fluctuations, details regarding the fluctuations of Greenlandic alpine glaciers prior to the Little Ice Age remain deficient. The early Holocene is a useful period to study alpine glacier response to rapid climate change as numerous abrupt climate events occurred during that time. We dated local glacier moraines on Nuussuaq in central West Greenland using ¹⁰Be dating of moraine boulders. Our updated chronology sets moraine emplacement at 10.4 ± 0.2 ka (n=5), suggesting that alpine glaciers experienced an advance or stillstand immediately after becoming independent during local deglaciation of this area at 10.5 ± <0.1 ka (n=2). A number of other Northern Hemisphere moraine chronologies from areas including the Alps, Scandinavia, Southern Norway, and potentially Baffin Island date to approximately 10.5-10.3 ka. This suggests the alpine glacier moraines from our study area document a response to regional climate forcing and are not simply a function of intrinsic climate variability. Based on moraine morphology, we also estimate paleotemperature values for 10.4 ka. A minimum paleo-equilibrium line altitude (ELA) value was determined using the maximum lateral moraine elevation (611 m asl). A ‘modern’ ELA estimate was determined using Landsat 7 satellite imagery from August of 2002 and an ASTER digital elevation model (834 m asl). By combining the difference between ELA values with an adiabatic lapse rate of 4.9°C/km from Gardner et al. (2009) and assuming no major changes in precipitation, we estimate a minimum average temperature approximately 1.1 ± 0.1°C lower at 10.4 ka than in 2002.