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Age-Depth Stratigraphy of Pine Island Glacier Inferred from Airborne Radars and Ice-Core Chronology
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  • Julien A Bodart,
  • Robert G Bingham,
  • David Ashmore,
  • Nanna B. Karlsson,
  • Andrew Hein,
  • David Vaughan
Julien A Bodart
University of Edinburgh

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Robert G Bingham
University of Edinburgh
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David Ashmore
University of Liverpool
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Nanna B. Karlsson
Geological Survey of Denmark and Greenland
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Andrew Hein
University of Edinburgh
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David Vaughan
British Antarctic Survey
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Understanding the contribution of the West Antarctic Ice Sheet (WAIS) to past and future sea level has emerged as a scientific priority over the last three decades. In recent years, observed thinning and ice-flow acceleration of the marine-based Pine Island Glacier has demonstrated that dynamic changes are central to the long-term stability of the WAIS. However, significantly less is known about the evolution of the catchment during the Holocene. Internal Reflecting Horizons (IRHs) provide a cumulative record of accumulation, basal melt and ice dynamics that, if dated, can be used to inform ice flow models to project spatial and temporal mass changes. Here, we use airborne radars to trace four consistent IRHs spanning the Holocene across the Pine Island Glacier catchment. We use the WAIS Divide ice-core chronology to assign discrete ages to three IRHs: 4.72 ± 0.08, 6.94 ± 0.11, and 16.50 ± 0.62 ka. We use a 1D model, constrained by observational and modelled accumulation rates, to produce an independent validation of our ice-core-derived ages and provide an age estimate for our shallowest IRH (2.31-2.92 ka). We find that significantly older ice is present below our deepest reflector, but the absence of continuous radar-observed reflectors at depth currently limits our understanding of pre-Holocene ice dynamical history. The clear correspondence between our IRH package and the one previously identified over Institute Ice Stream, altogether representing ~20% of the WAIS, suggests that a unique set of stratigraphic markers spanning the Holocene exist widely across West Antarctica.