THE RETREAT OF THE LAURENTIDE ICE SHEET IN RESPONSE TO RAPID WARMING AND ABRUPT COLD SPELLS IN THE EARLY HOLOCENE: AN ANALOG FOR PRESENT-DAY GREENLAND

The Greenland Ice Sheet (GIS) is currently a topic of much geologic interest. Because of the current warming trend seen across the globe, interest has focused on its melt rate and projections of future melt. But current projections are coarse, in part because of our inability to know how fast it can retreat. This therefore hinders our ability to foresee how fast it will retreat. This research attempts to shed light on the future melt of the GIS by looking at past ice sheet melt, and put it in the longer-term context of ice sheet retreat rates. Here we look at the deglaciation of the Laurentide Ice Sheet in Sam Ford Fiord, NE Baffin Island, during the early Holocene. The early Holocene on Baffin was marked by the Holocene Thermal Maximum (~10 to 8.5 ka), and by abrupt cold snaps like the 8.2 ka event, which brought significantly cooler temperatures to the Arctic for brief intervals. At this time though, it is not well known how Laurentide outlet glaciers within the fiords responded during this volatile climatic period. The study employs the use of 10Be and radiocarbon dating to constrain the timing and pattern of early Holocene deglaciation. Samples were collected along a transect from the mouth to the head of the fiord, spanning ~150 km. 22 samples were collected for 10Be dating, and 5 bivalve samples from raised marine deltas were collected for radiocarbon dating. Samples are currently being processed, and ages will be reported. A single 10Be age from an island in the mouth of Sam Ford Fiord collected during a previous field season suggests that ice was still present at the fiord mouth as late as ~9.5 ka. Radiocarbon ages from the fiord head generated in the 1960's imply that the fiord was ice free by ~7 ka. We will attempt to provide a detailed chronology of the retreat within this time range. The early-Holocene warming that took place on Baffin Island is similar to the present day warming that is affecting the GIS today. A tightly constrained deglaciation record for Sam Ford Fiord may be an analog for the future response of Greenland glaciers to current warming, and therefore may allow us to make more accurate predictions of the GIS's future contribution to global sea level rise.