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| Titel |
Characterizing the dynamics of a slowly surging glacier using a two-dimensional flowband model |
| VerfasserIn |
Gwenn Flowers, Nicolas Roux, Sam Pimentel |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040138
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| Zusammenfassung |
| Glacier surges are a well-known example of an internal dynamic oscillation whose
occurrence appears generally unconnected to the external climate forcing, but whose
character (e.g. period, mechanism) may depend on the glacier’s environmental or climate
setting. We examine the dynamics of a small (~5 km2) valley glacier in the Yukon Territory
of Canada for which two previous surges have been photographically documented and that
is thought to be currently surging, but at a much slower pace than ordinary. To
characterize the unusual dynamics of the present surge, and to speculate on the
future dynamics of this glacier, we employ a higher-order flowband model of ice
dynamics with a Coulomb-friction sliding law in both diagnostic and prognostic
simulations. Diagnostic (force balance) calculations capture the measured ice-surface
velocity profile only when high basal water pressures (60–90% of flotation) are
prescribed over the central region of the glacier, consistent with where evidence of
the surge has been identified. This leads to sliding accounting for 50–100% of the
total surface motion. Prognostic simulations, where the glacier geometry evolves
in response to a prescribed surface mass balance, reveal a significant role for a
large bedrock bump beneath the current equilibrium line of the glacier. This bump
provides resistance to ice flow sufficient to cause the formation, and under some
conditions propagation, of a bulge in the ice-surface profile. We suggest that this
bedrock bump contributes to the propensity for surges in this glacier, such that
conditions suppressing bulge formation may also inhibit surges. In our calculations
such a situation arises for sufficiently negative mass balance profiles. Collectively,
these results corroborate our interpretation of the current glacier flow regime as
indicative of a “slow surge”, and suggest 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 is observed in many other glacier
systems. |
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