Preprints
https://doi.org/10.5194/tc-2020-349
https://doi.org/10.5194/tc-2020-349

  02 Dec 2020

02 Dec 2020

Review status: a revised version of this preprint was accepted for the journal TC and is expected to appear here in due course.

Simulating the internal structure of the Antarctic Ice Sheet – towards a spatio-temporal calibration for ice-sheet modelling

Johannes Sutter1, Hubertus Fischer1, and Olaf Eisen2,3 Johannes Sutter et al.
  • 1Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • 2Alfred Wegener Institute Helmholtz-Centre for Polar and Marine Research, Bremerhaven, Germany
  • 3Department of Geosciences, University of Bremen, Bremen, Germany

Abstract. Ice Sheet Models are a powerful tool to project the evolution of the Greenland and Antarctic Ice Sheets, and thus their future contribution to global sea-level changes. Probing the fitness of ice-sheet models to reproduce ongoing and past changes of the Greenland and Antarctic ice cover is a fundamental part of every modelling effort. However, benchmarking ice-sheet model data against real-world observations is a non-trivial process, as observational data comes with spatio-temporal gaps in coverage. Here, we present a new approach to assess the ability of ice-sheet models which makes use of the internal layering of the Antarctic Ice Sheet. We simulate observed isochrone elevations within the Antarctic Ice Sheet via passive Lagrangian tracers, highlighting that a good fit of the model to two dimensional datasets does not guarantee a good match against the three dimensional architecture of the ice-sheet and thus correct evolution over time. We show, that paleoclimate forcing schemes commonly used to drive ice-sheet models work well in the interior of the Antarctic Ice Sheet and especially along ice divides, but fail towards the ice-sheet margin. The comparison to isochronal horizons attempted here reveals, that simple heuristics of basal drag can lead to an overestimation of the vertical interior ice sheet flow especially over subglacial basins. Our model-observation intercomparison approach opens a new avenue to the improvement and tuning of current ice-sheet models via a more rigid constraint on model parameterisations and climate forcing which will benefit model-based estimates of future and past ice-sheet changes.

Johannes Sutter et al.

 
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Johannes Sutter et al.

Video supplement

90 ka Antarctic tracers. Johannes Sutter https://doi.org/10.5446/50125

Johannes Sutter et al.

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Short summary
Projections of global sea level changes in a warming world require ice sheet models. We expand the calibration of these models by making use of the internal architecture of the Antarctic Ice Sheet which is formed by its evolution over many millennia. We propose that using our novel approach to constrain ice sheet models we will be able to both sharpen our understanding of past and future sea level changes and identify weaknesses in the parameterisation of current continental scale models.