Abstract
Abstract. Recent satellite data have revealed widespread grounding line retreat, glacier thinning, and associated mass loss along the Bellingshausen Sea sector, leading to increased concern for the stability of this region of Antarctica. While satellites have greatly improved our understanding of surface conditions, a lack of radio-echo sounding (RES) data in this region has restricted our analysis of subglacial topography, ice thickness, and ice flux. In this paper we analyse 3000 km of 150 MHz airborne RES data collected using the PASIN2 radar system (flown at 3–5 km line spacing) to investigate the subglacial controls on ice flow near the grounding lines of Ers, Envisat, Cryosat, Grace, Sentinel, Lidke, and Landsat ice streams as well as Hall and Nikitin glaciers. We find that each outlet is topographically controlled, and when ice thickness is combined with surface velocity data from MEaSUREs (Mouginot et al., 2019a), these outlets are found to discharge over 39.25 ± 0.79 Gt a−1 of ice to floating ice shelves and the Southern Ocean. Our RES measurements reveal that outlet flows are grounded more than 300 m below sea level and that there is limited topographic support for inland grounding line re-stabilization in a future retreating scenario, with several ice stream beds dipping inland at ∼ 5∘ km−1. These data reinforce the importance of accurate bed topography to model and understand the controls on inland ice flow and grounding line position as well as overall mass balance and sea level change estimates. RES data described in this paper are available through the UK Polar Data Centre: https://doi.org/10.5285/E07D62BF-D58C-4187-A019-59BE998939CC (Corr and Robinson, 2020).
Highlights
Remote sensing satellites have increased our awareness and understanding of ice flows in Antarctica since their inception
Close to the grounding line, Ers Ice Stream reaches a maximum flow speed of just over 940 m a−1 (Mouginot et al, 2019a). This ice originates from central Palmer Land (Fig. 1), where ice flows across the west of the Antarctic Peninsula, towards Ers Ice Stream
As ice flows through this channel, towards the local grounding line, ice thickness reduces from a maximum of ∼ 1400 m to between 580 and 610 m, where the ice flow is grounded ∼ 400 m below sea level
Summary
Remote sensing satellites have increased our awareness and understanding of ice flows in Antarctica since their inception. In western Palmer Land, on the Antarctic Peninsula, Earth observation satellites have recorded widespread grounding line retreat (Christie et al, 2016; Konrad et al, 2018) and surface lowering (attributed to glacier thinning) in the last 2 decades (Wouters et al, 2015; Hogg et al, 2017; Smith et al, 2020), as well as surface velocity increases and significant mass loss While satellites have greatly improved our understanding of surface conditions and changes across Antarctica in recent years, a lack of ice thickness and subglacial topographic measurements in western Palmer Land has restricted our analysis of the controls on ice flow, ice flux, and grounding line stability along the English Coast (Minchew et al, 2018). In this paper we present a new, freely available RES dataset along the English Coast of western Palmer Land, where several outlet glaciers were named after Earth observation satellites in 2019, in deference to the critical role
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