Glacier dynamics and paleoclimatic change during the last glaciation of eastern Ellesmere Island, Canada

摘要: A 300 km transect along the east coast of Ellesmere Island fills a major gap in the late Quaternary data base of the Canadian High Arctic. The last glacial maximum (LGM) is marked by prominent moraines and meltwater channels that terminate within 30 km of modern ice margins. Shells in glaciomarine deposits, collected beyond the LGM, indicate deglaciation by more extensive ice prior to 35 ka BP. More than 60 14C dates from glaciomarine sediments provide a chronology for past ice dynamics during the LGM. To the north, while many areas remained ice free due to severe aridity, several glaciers remained in contact with the sea until 7.1 ka BP. Farther south, most glaciers reached the coast and significantly infilled several fiords. This southward increase in glacier extent is due to larger glacial catchment basins and increased precipitation towards storm tracks in northern Baffin Bay. The earliest dates on deglaciation along the transect range from 8.1 to 7.7 ka BP. Initial retreat was controlled by the extent of the marine-based ice margins, which were destabilized by calving. Once landward of the sea, many glaciers stabilized until ~6.5 ka BP. Considerable interfiord variability in glacier dynamics is apparent. A paleoclimatic model is proposed linking past glacier activity in the Canadian High Arctic with the available ice core record. Greenland ice cores show that colder intervals, with depleted δ18O, were associated with reduced precipitation and storminess, which may have constrained ice buildup prior to ~15 ka BP. In contrast, the abrupt rise in δ18O after ~15 ka signals the onset of regional warming associated with increased storminess and precipitation (up to 200%). This may have occasioned a late buildup of High Arctic glaciers, which remained close to the last ice limit well into the Holocene.