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| Titel |
The sensitivity of flowline models of tidewater glaciers to parameter uncertainty |
| VerfasserIn |
E. M. Enderlin, I. M. Howat, A. Vieli |
| 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 (2013-10-07), S.1579-1590 |
| Datensatznummer |
250085169
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| Publikation (Nr.) |
 copernicus.org/tc-7-1579-2013.pdf |
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| Zusammenfassung |
| Depth-integrated (1-D) flowline models have been widely used to simulate
fast-flowing tidewater glaciers and predict change because the continuous
grounding line tracking, high horizontal resolution, and physically based
calving criterion that are essential to realistic modeling of tidewater
glaciers can easily be incorporated into the models while maintaining high
computational efficiency. As with all models, the values for parameters
describing ice rheology and basal friction must be assumed and/or tuned
based on observations. For prognostic studies, these parameters are
typically tuned so that the glacier matches observed thickness and speeds at
an initial state, to which a perturbation is applied. While it is well know
that ice flow models are sensitive to these parameters, the sensitivity of
tidewater glacier models has not been systematically investigated. Here we
investigate the sensitivity of such flowline models of outlet glacier
dynamics to uncertainty in three key parameters that influence a glacier's
resistive stress components. We find that, within typical observational
uncertainty, similar initial (i.e., steady-state) glacier configurations can
be produced with substantially different combinations of parameter values,
leading to differing transient responses after a perturbation is applied. In
cases where the glacier is initially grounded near flotation across a basal
over-deepening, as typically observed for rapidly changing glaciers, these
differences can be dramatic owing to the threshold of stability imposed by
the flotation criterion. The simulated transient response is particularly
sensitive to the parameterization of ice rheology: differences in ice
temperature of ~ 2 °C can determine whether the
glaciers thin to flotation and retreat unstably or remain grounded on a
marine shoal. Due to the highly non-linear dependence of tidewater glaciers
on model parameters, we recommend that their predictions are accompanied by
sensitivity tests that take parameter uncertainty into account. |
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