The Cryosphere
www.the-cryosphere.net
1994-0416
1994-0424
4
1
2010
10.5194/tc-4-21-2010
http://www.the-cryosphere.net/4/21/2010/
http://www.the-cryosphere.net/4/21/2010/tc-4-21-2010.html
http://www.the-cryosphere.net/4/21/2010/tc-4-21-2010.pdf
21
34
2010-01-19
Geometric changes and mass balance of the Austfonna ice cap, Svalbard
G. Moholdt
geirmoh@geo.uio.no
J. O. Hagen
T. Eiken
T. V. Schuler
Department of Geosciences, University of Oslo, Box 1047 Blindern, 0316 Oslo, Norway
The dynamics and mass balance regime of the Austfonna ice cap, the largest
glacier on Svalbard, deviates significantly from most other glaciers in the
region and is not fully understood. We have compared ICESat laser altimetry,
airborne laser altimetry, GNSS surface profiles and radio echo-sounding data
to estimate elevation change rates for the periods 1983–2007 and 2002–2008.
The data sets indicate a pronounced interior thickening of up to 0.5 m y<sup>−1</sup>,
at the same time as the margins are thinning at a rate of 1–3 m y<sup>−1</sup>. The southern basins are thickening at a higher rate than the
northern basins due to a higher accumulation rate. The overall volume change
in the 2002–2008 period is estimated to be −1.3±0.5 km<sup>3</sup> w.e. y<sup>−1</sup>
(or −0.16±0.06 m w.e. y<sup>−1</sup>) where the entire net loss is
due to a rapid retreat of the calving fronts. Since most of the marine ice
loss occurs below sea level, Austfonna's current contribution to sea level
change is close to zero. The geodetic results are compared to in-situ mass
balance measurements which indicate that the 2004–2008 surface net mass
balance has been slightly positive (0.05 m w.e. y<sup>−1</sup>) though with large
annual variations. Similarities between local net mass balances and local
elevation changes indicate that most of the ice cap is slow-moving and not
in dynamic equilibrium with the current climate. More knowledge is needed
about century-scale dynamic processes in order to predict the future
evolution of Austfonna based on climate scenarios.
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