A 10Be chronology of lateglacial and Holocene mountain glaciation in the Scoresby Sund region, east Greenland: implications for seasonality during lateglacial time

Thirty-eight new cosmogenic (10Be) exposure ages from the Scoresby Sund region of east Greenland indicate that prominent moraine sets deposited by mountain glaciers date from 780 to 310 yr, approximately during the Little Ice Age, from 11 660 to 10 630 yr, at the end of the Younger Dryas cold interval or during Preboreal time, and from 13 010 to 11 630 yr, during lateglacial time. Equilibrium line altitudes (ELAs) interpreted from lateglacial to Early Holocene moraines indicate summertime cooling between ∼3.9 and 6.6 °C relative to today's value, much less than the extreme Younger Dryas cooling registered by Greenland ice cores (mean-annual temperatures of ∼15 °C colder than today's value). This apparent discrepancy between paleotemperature records supports the contention that Younger Dryas cooling was primarily a wintertime phenomenon. 10Be ages of lateglacial and Holocene moraines show that mountain glaciers during the Little Ice Age were more extensive than at any other time since the Early Holocene Epoch. In addition, 10Be ages of lateglacial moraines show extensive reworking of boulders with cosmogenic nuclides inherited from prior periods of exposure, consistent with our geomorphic observations and cosmogenic-exposure dating studies in other Arctic regions.