Geometry and ice dynamics of the Darwin–Hatherton glacial system, Transantarctic Mountains

Mette K Gillespie,John W Holt,Wendy Lawson,Donald D Blankenship,Brian Anderson,Wolfgang Rack,Duncan A Young

doi:10.1017/jog.2017.60

Abstract

ABSTRACTThe Darwin–Hatherton Glacial system (DHGS) connects the East Antarctic Ice Sheet (EAIS) with the Ross Ice Shelf and is a key area for understanding past variations in ice thickness of surrounding ice masses. Here we present the first detailed measurements of ice thickness and grounding zone characteristics of the DHGS as well as new measurements of ice velocity. The results illustrate the changes that occur in glacier geometry and ice flux as ice flows from the polar plateau and into the Ross Ice Shelf. The ice discharge and the mean basal ice shelf melt for the first 8.5 km downstream of the grounding line amount to 0.24 ± 0.05 km3 a−1 and 0.3 ± 0.1 m a−1, respectively. As the ice begins to float, ice thickness decreases rapidly and basal terraces develop. Constructed maps of glacier geometry suggest that ice drainage from the EAIS into the Darwin Glacier occurs primarily through a deep subglacial canyon. By contrast, ice thins to <200 m at the head of the much slower flowing Hatherton Glacier. The glaciological field study establishes an improved basis for the interpretation of glacial drift sheets at the link between the EAIS and the Ross Ice Sheet.

Highlights

Recent mass-balance studies have shown that Antarctica is losing mass, primarily as a result of accelerating outlet glaciers in the northern Antarctic Peninsula and Amundsen Sea coast of the West Antarctic Ice Sheet (WAIS) (King and others, 2012; Shepherd and others, 2012; McMillan and others, 2014; Wuite and others, 2015)
The position of the central Darwin Glacier grounding line was determined from spatial variations in the ice base reflection observed in a ground penetrating radar (GPR) profile collected along the center flowline in an upstream direction (Fig. 3a)
At the central grounding line, measurements show that the Darwin Glacier is ∼1050 m thick and resting on a bed located ∼925 m below sea level

Summary

Introduction

Recent mass-balance studies have shown that Antarctica is losing mass, primarily as a result of accelerating outlet glaciers in the northern Antarctic Peninsula and Amundsen Sea coast of the West Antarctic Ice Sheet (WAIS) (King and others, 2012; Shepherd and others, 2012; McMillan and others, 2014; Wuite and others, 2015). The along-flow varying extent of moraines and glacial drift sheets show that the behavior of the glaciers is affected by changes in both the EAIS and the Ross Ice Shelf, the latter of which receives two-thirds of its ice from the WAIS (Mercer, 1968; Bockheim and others, 1989; Denton and others, 1989a, b; Conway and others, 1999; Fahnestock and others, 2000; Bromley and others, 2010). The TAM outlet glaciers represent key areas for studying the past and present dynamic behavior of both Antarctic ice sheets

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