Open AccessMarine ice sheet dynamics: Hysteresis and neutral equilibrium
Author(s) -
Durand G.,
Gagliardini O.,
de Fleurian B.,
Zwinger T.,
Le Meur E.
Publication year - 2009
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008jf001170
Subject(s) - geology , ice sheet , ice shelf , ice divide , ice stream , bedrock , glacier , ice sheet model , geophysics , antarctic ice sheet , sea ice , cryosphere , geomorphology , mechanics , climatology , physics
The stability of marine ice sheets and outlet glaciers is mostly controlled by the dynamics of their grounding line, i.e., where the bottom contact of the ice changes from bedrock or till to ocean water. The last report of the Intergovernmental Panel on Climate Change has clearly underlined the poor ability of models to capture the dynamics of outlet glaciers. Here we present computations of grounding line dynamics on the basis of numerical solutions of the full Stokes equations for ice velocity, coupled with the evolution of the air ice– and sea ice–free interfaces. The grounding line position is determined by solving the contact problem between the ice and a rigid bedrock using the finite element code Elmer. Results of the simulations show that marine ice sheets are unstable on upsloping beds and undergo hysteresis under perturbation of ice viscosity, confirming conclusions from boundary layer theory. The present approach also indicates that a 2‐D unconfined marine ice sheet sliding over a downsloping bedrock does not exhibit neutral equilibrium. It is shown that mesh resolution around the grounding line is a crucial issue. A very fine grid size (<100 m spacing) is needed in order to achieve consistent results.