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| Titel |
Effect of higher-order stress gradients on the centennial mass evolution of the Greenland ice sheet |
| VerfasserIn |
J. J. Fürst, H. Goelzer, P. Huybrechts |
| 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. 1 ; Nr. 7, no. 1 (2013-02-01), S.183-199 |
| Datensatznummer |
250017411
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| Publikation (Nr.) |
 copernicus.org/tc-7-183-2013.pdf |
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| Zusammenfassung |
| We use a three-dimensional thermo-mechanically coupled model of the
Greenland ice sheet to assess the effects of marginal perturbations on
volume changes on centennial timescales. The model is designed to allow for
five ice dynamic formulations using different approximations to the force
balance. The standard model is based on the shallow ice approximation for
both ice deformation and basal sliding. A second model version relies on a
higher-order Blatter/Pattyn type of core that resolves effects from
gradients in longitudinal stresses and transverse horizontal shearing, i.e.
membrane-like stresses. Together with three intermediate model versions,
these five versions allow for gradually more dynamic feedbacks from membrane
stresses. Idealised experiments are conducted on various resolutions to
compare the time-dependent response to imposed accelerations at the marine
ice front. If such marginal accelerations are to have an appreciable effect
on total mass loss on a century timescale, a fast mechanism to transmit
such perturbations inland is required. While the forcing is independent of
the model version, inclusion of direct horizontal coupling allows the
initial speed-up to reach several tens of kilometres inland. Within one
century, effects from gradients in membrane stress alter the inland signal
propagation and transmit additional dynamic thinning to the ice sheet
interior. But the centennial overall volume loss differs only by some
percents from the standard model, as the dominant response is a diffusive
inland propagation of geometric changes. For the experiments considered,
this volume response is even attenuated by direct horizontal coupling. The
reason is a faster adjustment of the sliding regime by instant stress
transmission in models that account for the effect of membrane stresses.
Ultimately, horizontal coupling decreases the reaction time to perturbations
at the ice sheet margin. These findings suggest that for modelling the mass
evolution of a large-scale ice sheet, effects from diffusive geometric
adjustments dominate effects from successively more complete dynamic
approaches. |
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