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| Titel |
A quasi-analytical ice-sheet model for climate studies |
| VerfasserIn |
J. Oerlemans  |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 10, no. 4/5 ; Nr. 10, no. 4/5, S.441-452 |
| Datensatznummer |
250007845
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| Publikation (Nr.) |
 copernicus.org/npg-10-441-2003.pdf |
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| Zusammenfassung |
| A simple
quasi-analytical model is developed to study the response of ice-sheets to
climate change. The model is axisymmetrical and rests on a bed with a
constant slope. The mechanics are highly parameterised. The climatic
conditions are represented by the altitude of the runoff line. Above the
runoff line the accumulation rate is constant (but may depend on, for
instance, the ice-sheet size), below the runoff line the balance gradient
is constant. The ice-sheet may extend into the sea and can respond to
changes in sea level. At the grounding line the ice velocity is assumed to
be proportional to the water depth. For this set-up an explicit expression
for the total mass budget of the ice-sheet is derived. To illustrate the
properties and possibilities of the model, equilibrium states are analysed
and the response to periodic forcing is studied as well. The coupling of
mass balance and surface elevation of the ice-sheet leads to nonlinear
behaviour and branching of the equilibrium solutions. The qualitative
behaviour of the system is that of the cusp catastrophe. Nonlinear effects
are more pronounced when the slope of the bed is smaller. A case is
discussed in which two ice-sheets are coupled by making the altitude of
the runoff line dependent on the total area of the two ice-sheets. On two
continents, having a slightly different glaciation threshold, periodic
forcing of the altitude of the runoff line is imposed. It is shown that in
such a situation variations on a long time scale (two to three times the
period of the forcing) are introduced. Finally the model is forced by the
GISP d18O record for the last 120
000 years. For an appropriate choice of parameters the model simulates
well the waxing and waning of the Laurentide, Fennoscandian and Barentsz
ice-sheets. |
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