High mid-Holocene accumulation rates over West Antarctica inferred from a pervasive ice-penetrating radar reflector

• Main Authors: Bodart, Julien A., Bingham, Robert G., Young, Duncan A., MacGregor, Joseph A., Ashmore, David W., Quartini, Enrica, Hein, Andrew S., Vaughan, David G., Blankenship, Donald D.
• Format: Text
• Language: English
• Published: 2022
• Subjects: Antarctic; Pine Island Glacier; Ross Sea; Thwaites Glacier; Weddell; West Antarctic Ice Sheet; West Antarctica; Antarc*; Antarctica; ice core; Ice Sheet; Pine Island
• Online Access: https://doi.org/10.5194/tc-2022-199; https://tc.copernicus.org/preprints/tc-2022-199/

Modelling the past and future evolution of the West Antarctic Ice Sheet (WAIS) to atmospheric and ocean forcing is challenged by the availability and quality of observed palaeo-boundary conditions. Key potential data for reconstructing past ice-sheet processes on large spatial scales are Internal Reflecting Horizons (IRHs) detected by Radio-Echo Sounding (RES) techniques. When isochronal and dated at ice cores, IRHs can be used to determine palaeo-accumulation rates and patterns. Using a spatially extensive IRH over Pine Island Glacier, Thwaites Glacier, Institute and Möller Ice Streams, and a local layer approximation model, we infer mid-Holocene accumulation rates over the slow-flowing parts of these catchments for the past ~5000 years. By comparing our results with modern climate reanalysis models and observational syntheses, we estimate that accumulation rates over the Amundsen-Weddell-Ross divide were on average 18 % higher than modern rates during the mid-Holocene. However, no significant spatial changes in the accumulation pattern were observed. These higher mid-Holocene accumulation-rate estimates match previous palaeo-accumulation estimates from ice-core and targeted IPR surveys over the ice divide, and also coincide with periods of grounding-line re-advance during the Holocene over the Weddell and Ross Sea sectors. Our results highlight the need for ice-sheet models to account for time-varying accumulation rates across the WAIS during the Holocene to provide better estimates of its contribution to past sea-level rise.