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Other research product . 2018

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

Fürst, Johannes Jakob; Gillet-Chaulet, Fabien; Benham, Toby J.; Dowdeswell, Julian A.; Grabiec, Mariusz; Navarro, Francisco; Pettersson, Rickard; +8 Authors
Open Access
Published: 27 Sep 2018

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.

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Funded by
Global Glacier Mass Continuity
  • Funder: European Commission (EC)
  • Project Code: 320816
  • Funding stream: FP7 | SP2 | ERC
Ice2sea - estimating the future contribution of continental ice to sea-level rise
  • Funder: European Commission (EC)
  • Project Code: 226375
  • Funding stream: FP7 | SP1 | ENV
Related to Research communities
European Marine Science Marine Environmental Science : Estimating the future contribution of continental ice to sea-level rise
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