HOLOCENE GLACIAL HISTORY OF RENLAND, EAST GREENLAND, RECONSTRUCTED FROM LAKE SEDIMENTS

The spatial extent, timing, and interhemispheric relationship of climate events yield information on potential forcing mechanisms. Here, we present a record of Holocene glacial variability from the Renland Ice Cap (RIC) in the Scoresby Sund region (~71° N, 27° W) of East Greenland. In order to reconstruct past glacial activity, we cored two glacially fed lakes in series that currently receive meltwater and sediment from the RIC. We also cored one non-glacial (control) lake. We measured multiple proxies in each core, including magnetic susceptibility, grain size, and percent organic and inorganic carbon to identify changes in sedimentation indicating glacial expansion and contraction. Minimum-limiting radiocarbon dates from all three lakes suggest deglaciation of the region between 9-8 ka. The non-glacial lake shows relatively little variation throughout the Holocene in any of the proxies. In contrast, the glacially-fed lakes show multiple bands of gray lacustrine clayey-silt interpreted to be glacial in origin. Dates indicate that some of these glacial sediment influxes occurred in both glacially-fed lakes at, or shortly after ~6.3, 3.0, and 1.1 cal ka. These clayey-silt bands are separated by brown, organic-rich silt, suggestive of little or no glacial input. Thus, for much of the Holocene, particularly in the mid-Holocene, the RIC fed little or no meltwater into the lakes. The thickest and most prominent gray clay layer was deposited after A.D. 940 and continued until present. We interpret this sedimentation to reflect glacier expansion in response to the onset of the Little Ice Age. The prominence of this layer in comparison with earlier clay horizons, indicates that the Little Ice Age was the largest event of the Holocene at RIC. This conclusion is in agreement with other data from East Greenland that suggest restricted glacial extent until the late Holocene.