The Cryosphere Discussions
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http://www.the-cryosphere-discuss.net/2/275/2008/tcd-2-275-2008.pdf
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2008-05-05
The equilibrium flow and mass balance of the Taku Glacier, Alaska 1950–2006
M. S. Pelto
mspelto@nichols.edu
S. R. McGee
G. W. Adema
M. J. Beedle
M. M. Miller
K. F. Sprenke
M. Lang
Nichols College Dudley, MA 01571, USA
Glaciological and Arctic Sciences Institute, University of Idaho, Moscow ID 83843, USA
Institute of Geodesy, Universität der Bundeswehr, Werner Heisenberg Weg, 85577 Neubiberg, Germany
Geography Program, University of Northern British Columbia, 3333 University Way, Prince George, B.C. V2L 2R4, Canada
Denali National Park and Preserve, P.O. Box 9, Denali Park, AK 99755, USA
The Taku Glacier, Alaska has advanced 7.5 km since the late nineteenth
century, while all other primary outlet glaciers of the Juneau Icefield are
in retreat. The Juneau Icefield Research Program has completed field work on
the Taku Glacier annually since 1946. The collected observations of surface
mass balance, glacier velocity and glacier thickness at Profile IV 29 km
above the terminus and 4 km above the equilibrium line provide a means to
assess the equilibrium nature of the Taku Glacier. Velocity measured over a
twelve month span and annual summer velocity measurements completed at a
Profile IV from 1950–2006 indicate insignificant variations in velocity
seasonally or from year to year. The consistency of velocity over the
56-year period indicates that in the vicinity of the equilibrium line, the
flow of the Taku Glacier has been in an equilibrium state.
<br><br>
Surface mass balance was positive from 1946–1988 averaging +0.42 m a<sup>−1</sup>.
This led to glacier thickening. From 1988–2006 an important change has
occurred and annual balance has been −0.14 m a<sup>−1</sup>, and the glacier
thickness has ceased increasing along Profile IV.
<br><br>
Field measurements of ice depth and surface velocity allow calculation of
the volume flux at Profile IV. Volume flux is then compared with the surface
balance flux from the region of the glacier above Profile IV, determined
annually in the field. Above Profile IV the observed mean surface flux is
5.50×10<sup>8</sup> m<sup>3</sup>/a (±5%), while the calculated volume
flux range flowing through profile IV is 5.00–5.47×10<sup>8</sup> m<sup>3</sup>/a. The
mean surface flux has been greater than the volume flux, which has led to
slow thickening of the Taku Glacier up to 1988. The thickening has not led
to a change in the flow of Taku Glacier at Profile IV.
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