The Cryosphere
www.the-cryosphere.net
1994-0416
1994-0424
2
1
2008
10.5194/tc-2-33-2008
http://www.the-cryosphere.net/2/33/2008/
http://www.the-cryosphere.net/2/33/2008/tc-2-33-2008.html
http://www.the-cryosphere.net/2/33/2008/tc-2-33-2008.pdf
33
51
2008-04-07
Improving estimation of glacier volume change: a GLIMS case study of Bering Glacier System, Alaska
M. J. Beedle
beedlem@unbc.ca
M. Dyurgerov
W. Tangborn
S. J. S. Khalsa
C. Helm
B. Raup
R. Armstrong
R. G. Barry
National Snow and Ice Data Center, 449 UCB, University of Colorado – Boulder, CO 80309-0559, USA
Institute of Arctic and Alpine Research, 450 UCB, University of Colorado – Boulder, CO 80309-0450, USA
Department of Physical Geography & Quaternary Geology, Stockholm University, SE – 106 92 Stockholm, Sweden
HyMet Inc., 13629 Burma Rd. SW, Vashon Island, WA 98070, USA
Geography Program, University of Northern British Columbia, 3333 University Way, Prince George, B.C. V2N 4Z9, Canada
The Global Land Ice Measurements from Space (GLIMS) project has developed
tools and methods that can be employed by analysts to create accurate
glacier outlines. To illustrate the importance of accurate glacier outlines
and the effectiveness of GLIMS standards we conducted a case study on Bering
Glacier System (BGS), Alaska. BGS is a complex glacier system aggregated
from multiple drainage basins, numerous tributaries, and many accumulation
areas. Published measurements of BGS surface area vary from 1740 to 6200 km<sup>2</sup>,
depending on how the boundaries of this system have been defined.
Utilizing GLIMS tools and standards we have completed a new outline (3630 km<sup>2</sup>)
and analysis of the area-altitude distribution (hypsometry) of BGS
using Landsat images from 2000 and 2001 and a US Geological Survey
15-min digital elevation model. We compared this new hypsometry with
three different hypsometries to illustrate the errors that result from the
widely varying estimates of BGS extent. The use of different BGS
hypsometries results in highly variable measures of volume change and net
balance (<I>b<sub>n</sub></I>). Applying a simple hypsometry-dependent mass-balance model
to different hypsometries results in a <I>b<sub>n</sub></I> rate range of −1.0 to −3.1 m a<sup>−1</sup>
water equivalent (W.E.), a volume change range of −3.8 to −6.7 km<sup>3</sup> a<sup>−1</sup>
W.E., and a near doubling in contributions to sea level
equivalent, 0.011 mm a<sup>−1</sup> to 0.019 mm a<sup>−1</sup>. Current
inaccuracies in glacier outlines hinder our ability to correctly quantify
glacier change. Understanding of glacier extents can become comprehensive
and accurate. Such accuracy is possible with the increasing volume of
satellite imagery of glacierized regions, recent advances in tools and
standards, and dedication to this important task.
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