Conditions for a steady grounding line
Abstract
To investigate the conditions under which a marine ice sheet may adopt a steady state profile, a finite element model which solves the full Stokes equations has been developed. The position of the grounding line is fixed, but the air-ice free surface and ice-sea free surface are unknown and part of the solution that we are seeking. Steady state solutions are sought for a range of basal conditions, mass fluxes, sea levels and back pressures. We demonstrate that the number of steady state solutions can be restricted by verifying that the simulations satisfy two contact inequalities. The contact conditions reflect that for physically acceptable solutions, the compressive normal stress at the base of the grounded ice should exceed water pressure, and that the shelf surface should not get into contact with the bedrock. Violation of either conditions would result in grounding line migration. We show that when ice slides over the bedrock and for a given sea level, only one combination of mass flux, grounding line thickness and back pressure, satisfies the contact conditions. When ice is frozen to the bedrock, however, a range of mass fluxes, grounding line thicknesses and back pressures satisfies the contact conditions for a particular sea level. The implication of these results for the instability hypothesis of marine ice sheets is addressed.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFM.C42A..06N
- Keywords:
-
- 0726 Ice sheets;
- 0728 Ice shelves;
- 0774 Dynamics;
- 0776 Glaciology (1621;
- 1827;
- 1863);
- 0798 Modeling