Radiostratigraphy and surface accumulation history of the Amundsen-Weddell Ice Divide, West Antarctica

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Abstract. Recent ground-based radio-echo sounding (RES) surveys across the Ellsworth Subglacial Highlands (ESH), a topographically complex region near the Amundsen–Weddell ice divide, reveal new insights into Holocene accumulation and ice dynamics in West Antarctica. We traced seven internal reflection horizons (IRHs) across approximately 2000 km of RES data spanning a 13,000 km2 area in the upper catchments of Pine Island Glacier, and the Rutford and Institute Ice Streams. Two of these IRHs intersect dated airborne radar lines tied to the WAIS Divide 2014 ice-core chronology. Applying the Dansgaard–Johnsen model with local accumulation rates from stake measurements and satellite-derived value we estimated ages of up to ~ 17.6 kyr for the deepest horizon (IRH7). Internal stratigraphy is well preserved in the slow-flowing alpine terrain of the ESH but becomes disrupted in areas of relatively fast flow and tributary convergence, such as the southern Ellsworth and CECs troughs. Despite these localised disturbances, IRHs remain traceable across most of the region, highlighting the potential for radiostratigraphic continuity in complex settings. Modern and Holocene accumulation patterns reveal a persistent asymmetry across the AWID, with consistently higher accumulation in the CECs Trough, supporting long-term ice divide stability since at least the mid-Holocene. Our study extends the spatial coverage of dated radiostratigraphy in West Antarctica and provides new linkage between the Weddell and Amundsen Sea Embayments. These results support several core goals of the AntArchitecture initiative of the Scientific Committee on Antarctic Research, including the expansion of a continent-wide IRH framework, improved Holocene accumulation reconstructions, identification of palaeoclimate archive targets, and enhanced boundary conditions for numerical ice-sheet models.

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