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| Titel |
Present dynamics and future prognosis of a slowly surging glacier |
| VerfasserIn |
G. E. Flowers, N. Roux, S. Pimentel, C. G. Schoof |
| 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 ; 5, no. 1 ; Nr. 5, no. 1 (2011-03-31), S.299-313 |
| Datensatznummer |
250002288
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| Publikation (Nr.) |
 copernicus.org/tc-5-299-2011.pdf |
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| Zusammenfassung |
| Glacier surges are a well-known example of an internal dynamic oscillation whose occurrence
is not a direct response to the external climate forcing, but whose character (i.e. period,
amplitude, mechanism) may depend on the glacier's environmental or climate setting.
We examine the dynamics of a small (∼5 km2) valley glacier in Yukon, Canada,
where two previous surges have been photographically documented and an unusually slow surge
is currently underway. To characterize the dynamics of the present surge, and to speculate
on the future of this glacier, we employ a higher-order flowband model of ice dynamics with
a regularized Coulomb-friction sliding law in both diagnostic and prognostic simulations.
Diagnostic (force balance) calculations capture the measured ice-surface velocity profile
only when non-zero basal water pressures are prescribed over the central region
of the glacier, coincident with where evidence of the surge has been identified. This leads
to sliding accounting for 50–100% of the total surface motion in this region.
Prognostic simulations, where the glacier geometry evolves in response to a prescribed surface
mass balance, reveal a significant role played by a bedrock ridge beneath the current equilibrium line of
the glacier. Ice thickening occurs above the ridge in our simulations, until
the net mass balance reaches sufficiently negative values. We suggest that the bedrock ridge
may contribute to the propensity for surges in this glacier by promoting the development of
the reservoir area during quiescence, and may permit surges to occur under more negative balance
conditions than would otherwise be possible. Collectively, these results corroborate our
interpretation of the current glacier flow regime as indicative of a slow surge that has been
ongoing for some time, and support a relationship between surge incidence or character and the
net mass balance. Our results also highlight the importance of glacier bed topography in
controlling ice dynamics, as observed in many other glacier systems. |
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