Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography

Oliver T. Bartlett*, Steven J. Palmer, Dustin M. Schroeder, Emma J. Mackie, Timothy T. Barrows, Alastair G. C. Graham

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Airborne radio-echo sounding (RES) surveys are widely used to measure ice-sheet bed topography. Measuring bed topography as accurately and widely as possible is of critical importance to modelling ice dynamics and hence to constraining better future ice response to climate change. Measurement accuracy of RES surveys is influenced both by the geometry of bed topography and the survey design. Here we develop a novel approach for simulating RES surveys over glaciated terrain, to quantify the sensitivity of derived bed elevation to topographic geometry. Furthermore, we investigate how measurement errors influence the quantification of glacial valley geometry. We find a negative bias across RES measurements, where off-nadir return measurement error is typically -1.8 ± 11.6 m. Topographic highlands are under-measured an order of magnitude more than lowlands. Consequently, valley depth and cross-sectional area are largely under-estimated. While overall estimates of ice thickness are likely too high, we find large glacier valley cross-sectional area to be under-estimated by -2.8 ± 18.1%. Therefore, estimates of ice flux through large outlet glaciers are likely too low when this effect is not taken into account. Additionally, bed mismeasurements potentially impact our appreciation of outlet-glacier stability.

Original languageEnglish
Number of pages12
JournalAnnals of Glaciology
Early online date28 May 2020
DOIs
Publication statusEarly online - 28 May 2020

Keywords

  • Glaciological instruments and methods
  • Greenland Ice Sheet
  • radio-echo sounding
  • subglacial topography
  • RCUK
  • NERC
  • NE/L002434/1

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