GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 54-4
Presentation Time: 2:30 PM


CRUMP, Sarah E., Geological Sciences and Institute of Arctic and Alpine Research, University of Colorado – Boulder, Boulder, CO 80309, YOUNG, Nicolás E., Lamont-Doherty Earth Observatory, Columbia University, 219 Comer, 61 Route 9W - PO Box 1000, Palisades, NY 10964-8000, PENDLETON, Simon L., Geological Sciences and Institute of Arctic and Alpine Research, University of Colorado – Boulder, Boulder, CO 80309; Woods Hole Oceanographic Institute, Woods Hole, MA 02543, MILLER, Gifford H., INSTAAR and Geological Sciences, University of Colorado, Boulder, CO 80309-0450, ANDERSON, Robert S., Department of Geological Sciences and INSTAAR, University of Colorado, Boulder, CO 80309 and BRINER, Jason P., Department of Geology, University at Buffalo, 126 Cooke Hall, Buffalo, NY 14260

The North Atlantic was a key locus for circulation-driven abrupt climate change in the past and could play a similar role in the near future under anthropogenic climate change. Known abrupt cold reversals, including the 8.2 ka event, punctuated the otherwise warm early Holocene in the North Atlantic region, providing useful paleo examples of rapid climate change. In this work, we assess the cryospheric response to such centennial-scale coolings on Baffin Island, Arctic Canada, using cosmogenic nuclide exposure dating of moraines. We present 10Be ages from four sets of multi-crested moraines deposited by cirque glaciers and ice cap outlet glaciers during early Holocene. The age of one moraine is additionally constrained by in situ 14C dating, which confirms the presence of inherited 10Be inventories in some boulder samples. All four moraines were deposited between 9.4 and 8.0 ka, and their average ages statistically overlap with abrupt cooling events at 9.3 and 8.2 ka that have been previously documented in Greenland ice-core records. Relatively cold sea surface conditions in Baffin Bay before 8 ka may have contributed to cool baseline summer temperatures that were exacerbated by centennial-scale freshwater-forced cooling episodes. In addition, we use a numerical glacier model to explore mechanistic factors that may have contributed to these moraine-building events. Dynamic adjustment of tributary glacier profiles following deglaciation of trunk valley ice may have primed these systems to expand and deposit moraines during brief cold reversals. These new age constraints and process insights highlight the complex behavior of the cryosphere during regional deglaciation. The data support the hypothesis that reductions in northward heat transport by North Atlantic currents triggered multiple early Holocene cold reversals and associated glacier responses on Baffin Island.