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| Titel |
Solving the Momentum Equations of Dynamic Sea Ice Models with Implicit Solvers and the Elastic-Viscous-Plastic Technique |
| VerfasserIn |
M. Losch, S. Danilov |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022614
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| Zusammenfassung |
| The momentum equations that describe sea ice drift for a viscous-plastic (VP) ice
rheology are difficult to solve numerically, because the associated bulk and shear
viscosities can be very large. Traditionally, implicit solution techniques for the VP
rheology are thought to be expensive; the explicit elastic-viscous-plastic (EVP) method
was designed to be more efficient and accurate. In order to assess their relative
performance, experiments with idealized geometry are used to compare model solutions of
implicit VP- and explicit EVP-solvers in two very different ice-ocean codes: the
regular-grid, finite-volume Massachusetts Institute of Technology general circulation
model (MITgcm) and the Alfred Wegener Institute Finite Element Ocean Model
(FEOM). For both codes the obtained solutions of implicit VP- and EVP-solvers can
differ significantly, because the EVP solutions tend to have smaller ice viscosities
(“weaker” ice). EVP solutions tend to converge to implicit VP solutions for very small
sub-cycling time steps. A limiting scheme for EVP viscosities, that addresses a
noise problem, reduces the viscosity even further and, especially in the case of
the variable-resolution unstructured grids of FEOM, can lead to unexpected ice
distributions that are dramatically different from solutions without this scheme.
Implicit VP-solvers are found to be generally faster than the EVP-solvers, most likely
because the ice distribution does not change much within the short time steps of this
study. Short time steps are thought to be typical of present day high resolution
ice-ocean models, so that previous timing results for long time steps may no longer be
representative. |
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