Abstract. Ocean-induced basal melting is directly and indirectly responsible for much of the Amundsen Sea Embayment ice loss in recent decades, but the total magnitude and spatiotemporal evolution of this melt is poorly constrained. To address this problem, we generated a record of high-resolution Digital Elevation Models (DEMs) for Pine Island Glacier (PIG) using commercial sub-meter satellite stereo imagery and integrated additional 2002–2015 DEM/altimetry data. We implemented a Lagrangian elevation change (Dh/Dt) framework to estimate ice shelf basal melt rates at 32–256-m resolution. We describe this methodology and consider basal melt rates and elevation change over the PIG shelf and lower catchment from 2008–2015. We document the evolution of Eulerian elevation change (dh/dt) and upstream propagation of thinning signals following the end of rapid grounding line retreat around 2010. Mean full-shelf basal melt rates for the 2008–2015 period were ~82–93 Gt/yr, with ~ 200–250 m/yr basal melt rates within large channels near the grounding line, ~ 10–30 m/yr over the main shelf, and ~ 0–10 m/yr over the North and South shelves, with the notable exception of a small area with rates of ~ 50–100 m/yr near the grounding line of a fast-flowing tributary on the South shelf. The observed basal melt rates show excellent agreement with, and providemore »
High-resolution sub-ice-shelf seafloor records of twentieth century ungrounding and retreat of Pine Island Glacier, West Antarctica: HIGH-RESOLUTION SUB-ICE-SHELF SEAFLOOR IMAGERY
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Abstract. In the 2019/2020 austral summer, the surface melt duration andextent on the northern George VI Ice Shelf (GVIIS) was exceptional comparedto the 31 previous summers of distinctly lower melt. This finding is basedon analysis of near-continuous 41-year satellite microwave radiometer andscatterometer data, which are sensitive to meltwater on the ice shelfsurface and in the near-surface snow. Using optical satellite imagery fromLandsat 8 (2013 to 2020) and Sentinel-2 (2017 to 2020), record volumes ofsurface meltwater ponding were also observed on the northern GVIIS in2019/2020, with 23 % of the surface area covered by 0.62 km3 of ponded meltwater on 19 January. These exceptional melt andsurface ponding conditions in 2019/2020 were driven by sustained airtemperatures ≥0 ∘C for anomalously long periods (55 to 90 h)from late November onwards, which limited meltwater refreezing.The sustained warm periods were likely driven by warm, low-speed (≤7.5 m s−1) northwesterly and northeasterly winds and not by foehn windconditions, which were only present for 9 h total in the 2019/2020 meltseason. Increased surface ponding on ice shelves may threaten theirstability through increased potential for hydrofracture initiation; a riskthat may increase due to firn air content depletion in response tonear-surface melting.
