Holocene glacial evolution in Quingaussarsuaq Peninsula (Central-West Greenland)

초록

The Greenland Ice Sheet (GrIS) is a key component of the global climate system, and constraining the Holocene deglaciation history of its land-terminating margins is key to understanding its sensitivity to climate forcing. Here, we provide insights into landscape evolution and environmental change on the Qinguassarsuaq Peninsula, Central-West Greenland 69 degrees N, 50 degrees W, where we used high-resolution geomorphological surveys and extensive field mapping to identify features formed during ice retreat. We divided the peninsula into four principal geomorphological units: elevated uplands, glacial valleys, nunataks, and active glacial outlets. We then established the timeline of deglaciation using Be-10 cosmic-ray exposure (CRE) dating of 20 samples collected from well-preserved glacially polished bedrock and stable moraine boulders, together with four optically stimulated luminescence (OSL) ages from glaciofluvial terraces formed by ice-marginal damming. Geomorphological evidence indicated that ice occupied the valleys and plateaus of the peninsula and overtopped nearby summits during the Late Pleistocene. Four OSL ages from lacustrine terraces spanning 20.8-8.3 ka indicated deglaciation of the area by the Early Holocene. As the GrIS thinned at this time, ice retreat confined the ice mass to the eastern fringe of the peninsula, where deglaciation progressed between similar to 8.0 and 6.5 ka, also exposing the nunataks that today rise above the ice sheet. Near the present glacier front, CRE ages of similar to 0.9-1.0 ka from several lateral and frontal moraines suggested a general absence of major Neoglacial re-advances, apart from the last millennium, including ice expansion during the late Mediaeval Warm Period to the early Little Ice Age. Our results underscore the importance of integrating geomorphological mapping with multiple dating techniques to refine reconstructions of the GrIS's complex deglaciation history.

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