Application of a two-step approach for mapping ice thickness to various glacier types on Svalbard

Fürst J, Gillet-Chaulet F, Benham T, Dowdeswell J, Grabiec M, Navarro FJ, Pettersson R, Moholdt G, Nuth C, Saß B, Aas K, Fettweis X, Lang C, Seehaus T, Braun M (2017)

Publication Language: English

Publication Type: Journal article, Original article

Publication year: 2017

Journal

Book Volume: 11

Pages Range: 2003-2032

Journal Issue: 5

DOI: 10.5194/tc-11-2003-2017

Open Access Link: https://www.the-cryosphere.net/11/2003/2017/tc-11-2003-2017.html

Abstract

The basal topography is largely unknown beneath most glaciers and ice caps, and many attempts have been made to estimate a thickness field from other more accessible information at the surface. Here, we present a two-step reconstruction approach for ice thickness that solves mass conservation over single or several connected drainage basins. The approach is applied to a variety of test geometries with abundant thickness measurements including marine- and land-terminating glaciers as well as a 2400 km² ice cap on Svalbard. The input requirements are kept to a minimum for the first step. In this step, a geometrically controlled, non-local flux solution is converted into thickness values relying on the shallow ice approximation (SIA). In a second step, the thickness field is updated along fast-flowing glacier trunks on the basis of velocity observations. Both steps account for available thickness measurements. Each thickness field is presented together with an error-estimate map based on a formal propagation of input uncertainties. These error estimates point out that the thickness field is least constrained near ice divides or in other stagnant areas. Withholding a share of the thickness measurements, error estimates tend to overestimate mismatch values in a median sense. We also have to accept an aggregate uncertainty of at least 25 % in the reconstructed thickness field for glaciers with very sparse or no observations. For Vestfonna ice cap (VIC), a previous ice volume estimate based on the same measurement record as used here has to be corrected upward by 22 %. We also find that a 13 % area fraction of the ice cap is in fact grounded below sea level. The former 5 % estimate from a direct measurement interpolation exceeds an aggregate maximum range of 6–23 % as inferred from the error estimates here.

Authors with CRIS profile

Involved external institutions

Norsk Polarinstitutt / Norwegian Polar Institute Norway (NO) University of Oslo Norway (NO)

How to cite

APA:

Fürst, J., Gillet-Chaulet, F., Benham, T., Dowdeswell, J., Grabiec, M., Navarro, F.J.,... Braun, M. (2017). Application of a two-step approach for mapping ice thickness to various glacier types on Svalbard. Cryosphere, 11(5), 2003-2032. https://doi.org/10.5194/tc-11-2003-2017

MLA:

Fürst, Johannes, et al. "Application of a two-step approach for mapping ice thickness to various glacier types on Svalbard." Cryosphere 11.5 (2017): 2003-2032.

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