New in situ14C data indicate the absence of nunataks in west Greenland during the Last Glacial Maximum

Abstract

In situ cosmogenic nuclide exposure age distributions on Ice Age nunataks act as past ice thickness indicators and provide valuable targets for ice sheet model simulations of the Last Glacial Maximum. Several locations along West Greenland have been identified as being potential nunataks due to their weathered nature and their high cosmogenic nuclide inventories with little evidence for ice sheet burial. We present new in situ cosmogenic 14C measurements from four high elevation surfaces in the central Uummannaq Fjord system that were identified as potential nunataks in prior work. Building on previous work, we model cosmogenic radionuclide production and decay, and consider a range of ice sheet history scenarios. Since our results require more burial or shielding under ice than what independent methods suggest for Holocene ice cap cover, we propose that these locations were not nunataks during the Last Glacial Maximum, but rather were buried during the peak of the Last Glacial Maximum. However, we cannot confirm whether these sites were buried by the Greenland Ice Sheet or local glaciers.