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| Titel |
A note on the water budget of temperate glaciers |
| VerfasserIn |
J. Oerlemans  |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 7, no. 5 ; Nr. 7, no. 5 (2013-09-27), S.1557-1564 |
| Datensatznummer |
250085167
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| Publikation (Nr.) |
 copernicus.org/tc-7-1557-2013.pdf |
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| Zusammenfassung |
In this note, the total dissipative melting in temperate glaciers is studied.
The analysis is based on the notion that the dissipation is determined by
the loss of potential energy due to the downward motion of mass (ice, snow,
meltwater and rain). A mathematical formulation of the dissipation is
developed and applied to a simple glacier geometry. In the next step,
meltwater production resulting from enhanced ice motion during a glacier
surge is calculated. The amount of melt energy available follows directly
from the lowering of the centre of gravity of the glacier.
To illustrate the concept, schematic calculations are presented for a number
of glaciers with different geometric characteristics. Typical dissipative
melt rates, expressed as water-layer depth averaged over the glacier, range
from a few centimetres per year for smaller glaciers to half a metre per
year for Franz Josef Glacier, one of the most active glaciers in the world
(in terms of mass turnover).
The total generation of meltwater during a surge is typically half a metre.
For Variegated Glacier a value of 70 cm is found, for Kongsvegen 20 cm.
These values refer to water layer depth averaged over the entire glacier. The
melt \textit{rate} depends on the duration of the surge. It is
generally an order of magnitude greater than water production by `normal'
dissipation. On the other hand, the additional basal melt rate during a surge
is comparable in magnitude with the water input from meltwater and
precipitation. This suggests that enhanced melting during a surge does not
grossly change the total water budget of a glacier. Basal water generated by
enhanced sliding is an important ingredient in many theories of glacier
surges. It provides a positive feedback mechanism that actually makes the
surge happen. The results found here suggest that this can only work if water
generated by enhanced sliding accumulates in a part of the glacier base
where surface meltwater and rain have no or very limited access. This finding
seems compatible with the fact that, on many glaciers, surges are initiated in
the lower accumulation zone. |
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