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| Titel |
A new approach for estimating ice thickness distribution of 90'000 mountain glaciers around the globe |
| VerfasserIn |
M. Huss, D. Farinotti |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062608
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| Zusammenfassung |
| Mass loss of mountain glaciers and small ice caps is an important component of eustatic
sea-level rise. The ice volume of these more than 100’000 glaciers is normally estimated
using volume-area scaling relationships. Volume-area scaling does, however, not account for
the characteristics of individual glaciers, and does not yield any information about the spatial
distribution of the ice thickness, which is required e.g. for the transient modelling of glacier
ice flow dynamics.
Here, we propose and apply a new method for adding the third dimension to glacier
inventories by inverting global digital elevation model (DEM) data to distributed ice
thickness. The method to estimate ice thickness distribution of mountain glaciers and small
ice caps around the globe is based on glacier mass turn-over and the principles of ice flow
mechanics. Using glacier elevation bands evaluated from a digital elevation model, volume
balance flux is calculated and transformed into local ice thickness using Glen’s flow law. In
an iterative procedure, the basal shear-stress distribution and the shape factor is determined.
Finally, mean thickness in each elevation band is extrapolated transversal to the topographic
gradient based on local surface slope. Thus, for each glacier ice thickness on a
regular grid can be calculated. The only input requirements are a glacier outline and a
DEM.
DEMs between 60°N and 60°S are available from the Shuttle Radar Topographic Mission
(SRTM) with a spatial resolution of about 90 m. North and South of 60° the Advanced
Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEM (30 m resolution)
is used. Glacier outlines are provided by the Global Land Ice Measurement from Space
(GLIMS). Based on these readily available data sets, thickness distribution and ice volume of
all 90’000 glaciers currently contained in the GLIMS database are evaluated. Application of
the method to all mountain glaciers and small ice caps around the globe provided by a
recently completed world glacier inventory is planned for estimating global glacier ice
volumes.
Inferred thickness distribution is validated against in-situ measurements (radio-echo
sounding) for about 50 glaciers across all continents, and against additional ice volume data.
Calculated ice thickness agrees well with field observations which supports the
worldwide applicability of the approach. Uncertainties are quantified, and we discuss the
potential of the new approach in comparison to traditional volume-area scaling. |
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