IMPLEMENTATION OF A VERTICALLY INTEGRATED ICE SHEET MOMENTUM BALANCE MODEL

A new high-fidelity ice sheet momentum balance model meant for inclusion in the Glimmer community ice-sheet model is presented. As a component of the Community Earth Systems Model the newly developed momentum balance will directly benefit from ice/ocean and ice/atmosphere coupling efforts occurring elsewhere. The objectives of this thesis are to develop a model which converges quickly (quadratic convergence rates) for non-Newtonian Stokes flow approximations, and to provide a clear and low-level discussion of its derivation, variation and discretization. The model utilizes the Finite Element Method to discretize variational forms of the first variation arising from the Galerkin method and for vertically-integrated Stokes flow. The model employs a hybridization of two commonly used approximations to Stokes flow. It couples the Shallow Shelf Approximation (SSA) and Shallow Ice Approximation (SIA). This approximation is then differentiated symbolically. Efficient sparse matrix formats are manipulated directly to avoid invoking costly sorting routines in the underlying linear solvers. The code was not only developed for standards-compliant FORTRAN 90 compilers but also for automatic differentiation tools. The model is verified against published model intercomparison projects.

Name thesis:degree_name

Master of Science (MS)

Grantor dc:publisher

University of Montana

Year

2013

Author dc:creator

• Campbell, Joshua Charles

• approximation
• discretization
• finite elements
• first variation
• fortran
• fortran 90
• galerkin
• ice sheet
• incompressible
• l1l2
• model
• momentum balance
• non-newtonian
• partial differential equations
• rheology
• sea-level rise
• shallow ice
• shallow shelf

Repository record dc:identifier

https://scholarworks.umt.edu/etd/552

OAI identifier oai:identifier

oai:scholarworks.umt.edu:etd-1571