Investigations to constrain retreat of the Greenland Ice Sheet: glacial geomorphology and sampling for cosmogenic exposure dating of the Centrumsø area, Kronprins Christian Land, northeast Greenland

Over the last few decades atmospheric warming across the Arctic has been far more rapid than elsewhere in the world, contributing to an increase in the sea-level contribution from the Greenland Ice Sheet. Given predictions of continuing atmospheric warming during the 21st century and beyond, it is crucial to understand how the ice sheet has responded to past variations in climate. Kronprins Christian Land lies in a climatically sensitive, yet sparsely studied part of northeast Greenland, in an inter-ice-stream region just north of Nioghalvfjerdsbrae. This paper presents the results of preliminary geomorphological mapping from a 2m spatial-resolution digital elevation model of a 5500km2; region around Centrumsø, as well as a report of sampling for cosmogenic exposure dating, and field observations concerning the extent and nature of palaeo-ice coverage and dynamics. Twenty-one 2kg samples were collected from carefully selected glacial erratics of various lithologies using a hammer and chisel as well as a small angle-grinder. In general, moraine ridges in the study area are relatively small (2–5m in height) and lack a prominent peak, reflecting limited sediment availability, and suggesting some post-glacial re-mobilization of sediment or deflation caused by melting of the moraines' ice cores. Striated cobbles and boulder-sized clasts were observed at up to 540m a.s.l., sub-rounded erratics (some of which were sampled) at up to 800m a.s.l. and streamlined bedrock at up to 360m a.s.l., all of which indicate sliding between the ice and the bedrock and temperate basal conditions. In addition, several proglacial spillways were noted, along with numerous terraces, commonly situated between lateral moraines and valley sides, which are probably kame terraces formed by glaciofluvial transport and deposition. The prevalence of these landforms indicates significant glaciofluvial action requiring large volumes of meltwater, suggesting this region experienced high-volume melt in short intensive summers during past ice-recession events

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Nienow, Sole and Cowton’s Greenland research has been supported by a number of UK NERC research grants (NER/O/S/2003/00620; NE/F021399/1; NE/H024964/1; NE/K015249/1; NE/K014609/1) and Slater has been supported by a NERC PhD studentshipPurpose of the review:  This review discusses the role that meltwater plays within the Greenland ice sheet system. The ice sheet’s hydrology is important because it affects mass balance through its impact on meltwater runoff processes and ice dynamics. The review considers recent advances in our understanding of the storage and routing of water through the supraglacial, englacial, and subglacial components of the system and their implications for the ice sheet Recent findings:   There have been dramatic increases in surface meltwater generation and runoff since the early 1990s, both due to increased air temperatures and decreasing surface albedo. Processes in the subglacial drainage system have similarities to valley glaciers and in a warming climate, the efficiency of meltwater routing to the ice sheet margin is likely to increase. The behaviour of the subglacial drainage system appears to limit the impact of increased surface melt on annual rates of ice motion, in sections of the ice sheet that terminate on land, while the large volumes of meltwater routed subglacially deliver significant volumes of sediment and nutrients to downstream ecosystems. Summary:  Considerable advances have been made recently in our understanding of Greenland ice sheet hydrology and its wider influences. Nevertheless, critical gaps persist both in our understanding of hydrology-dynamics coupling, notably at tidewater glaciers, and in runoff processes which ensure that projecting Greenland’s future mass balance remains challenging.Publisher PDFPeer reviewe