The age of ice exposed along the northern margin of the Greenland Ice Sheet
Abstract
Each summer, the ablation zone of the Greenland Ice Sheet exposes its distinctive surface stratigraphy, which is a function of variability in atmospheric dust concentration at the time of deposition and subsequent flow from the interior accumulation zone to the margin. Here we map and describe this surface stratigraphy across the underexplored northern margin of the ice sheet. We first mosaic Sentinel-2A multispectral satellite imagery of Greenland at the end of the 2016 melt season, when the ice-sheet ablation zone was relatively extensive. We supplement this mosaic with higher-resolution WorldView-2/3 imagery for regions of interest identified by Sentinel-2A. We then trace several distinct transitions in apparent dust concentration, which have been identified previously as representing late Pleistocene and Holocene climatic boundaries, to develop a coarse chronostratigraphy for the ice-sheet ablation zone north of 77ºN. Unusually dark mid-Holocene ice, previously identified in southwestern Greenland, is also found adjacent to Kronprins Christian Land in northeastern Greenland. The Prudhoe Lobe, adjacent to Smith Sound, contains the most extensive exposure of contiguous Holocene ice in northern Greenland. Recumbent folding of marginal ice is most common in northeastern Greenland. Unusually symmetric folding of pre-Holocene ice appears unique to the margin southwest of Hiawatha Glacier. The oldest conformal surface-exposed ice in northern Greenland is likely located within two kilometer-long portions of the margin adjacent to Warming Land. Based on a comparison with the NorthGRIP dust-concentration record, these exposures likely represent ice up to ~54 ka old. We conclude that northern Greenland offers better opportunities to recover paleoclimatically valuable ice from its margin than previously exploited regions in southwestern Greenland.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C11C1280M
- Keywords:
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- 0724 Ice cores;
- CRYOSPHERE;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1616 Climate variability;
- GLOBAL CHANGE;
- 4994 Instruments and techniques;
- PALEOCEANOGRAPHY