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You searched for subject:(shallow shelf approximation). Showing records 1 – 2 of 2 total matches.

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Delft University of Technology

1. van Dongen, Eef (author). Coupling approximation levels for modeling ice flow on paleo time scales.

Degree: 2017, Delft University of Technology

Ice flow, forced by gravity is governed by the Full Stokes (FS) equations, which are computationally intensive to solve due to their non-linearity. Therefore, it has been unavoidable to approximate the FS equations when modeling growth and collapse of an ice sheet-shelf system, which requires simulating many thousands of years. However, the most popular Shallow Ice Approximation (SIA) and Shallow Shelf Approximation (SSA) are only accurate in certain parts of an ice sheet, both excluding the grounding line where the ice starts floating. Using the Finite Element software Elmer/Ice, SIA and SSA are dynamically coupled to FS aiming to maintain high precision and reduce computation time. An existing coupling of SIA and FS, called ISCAL [Ahlkrona et al., 2013a], is investigated for robustness. It is shown that instabilities in the FS solution limit ISCAL’s robustness. A novel way of iteratively coupling SSA and FS has been implemented into the open source Finite Element software Elmer/Ice and applied to both 2D and 3D conceptual marine ice sheets. The SSA-FS coupling shows to be very accurate, for both diagnostic and prognostic runs (error in velocity respectively below 0.5% and 5%). Grounding line dynamics of the SSA-FS coupling are similar to the FS model under a periodical forcing in a simulation covering 3000 years. The current implementation does not yield speed up in 2D due to inefficient assembly of the matrices to be solved. In 3D, the cpu time is reduced to two thirds of the cpu time of the FS model despite inefficient assembly. The total number of FS iterations in the SSA-FS coupling is comparable to the FS model, showing a large potential of reducing computation time since computation time of the SSA model is up to 3% of the FS model’s computation time when applied to the same ice shelf ramp. In future research, the SSA-FS coupling can be combined with ISCAL, but this requires both efficient implementation of the SSA-FS coupling and improved stabilization methods for FS.

Applied Mathematics

Advisors/Committee Members: van Gijzen, Martin (mentor), Delft University of Technology (degree granting institution).

Subjects/Keywords: Finite Element Method; Ice sheet modeling; coupling approximations; full stokes; shallow shelf approximation; shallow ice approximation

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

van Dongen, E. (. (2017). Coupling approximation levels for modeling ice flow on paleo time scales. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:caed0f22-278b-4dc3-ac52-775a17706e3c

Chicago Manual of Style (16th Edition):

van Dongen, Eef (author). “Coupling approximation levels for modeling ice flow on paleo time scales.” 2017. Masters Thesis, Delft University of Technology. Accessed January 26, 2021. http://resolver.tudelft.nl/uuid:caed0f22-278b-4dc3-ac52-775a17706e3c.

MLA Handbook (7th Edition):

van Dongen, Eef (author). “Coupling approximation levels for modeling ice flow on paleo time scales.” 2017. Web. 26 Jan 2021.

Vancouver:

van Dongen E(. Coupling approximation levels for modeling ice flow on paleo time scales. [Internet] [Masters thesis]. Delft University of Technology; 2017. [cited 2021 Jan 26]. Available from: http://resolver.tudelft.nl/uuid:caed0f22-278b-4dc3-ac52-775a17706e3c.

Council of Science Editors:

van Dongen E(. Coupling approximation levels for modeling ice flow on paleo time scales. [Masters Thesis]. Delft University of Technology; 2017. Available from: http://resolver.tudelft.nl/uuid:caed0f22-278b-4dc3-ac52-775a17706e3c


University of Montana

2. Campbell, Joshua Charles. IMPLEMENTATION OF A VERTICALLY INTEGRATED ICE SHEET MOMENTUM BALANCE MODEL.

Degree: MS, 2013, University of Montana

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.

Subjects/Keywords: 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

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Campbell, J. C. (2013). IMPLEMENTATION OF A VERTICALLY INTEGRATED ICE SHEET MOMENTUM BALANCE MODEL. (Masters Thesis). University of Montana. Retrieved from https://scholarworks.umt.edu/etd/552

Chicago Manual of Style (16th Edition):

Campbell, Joshua Charles. “IMPLEMENTATION OF A VERTICALLY INTEGRATED ICE SHEET MOMENTUM BALANCE MODEL.” 2013. Masters Thesis, University of Montana. Accessed January 26, 2021. https://scholarworks.umt.edu/etd/552.

MLA Handbook (7th Edition):

Campbell, Joshua Charles. “IMPLEMENTATION OF A VERTICALLY INTEGRATED ICE SHEET MOMENTUM BALANCE MODEL.” 2013. Web. 26 Jan 2021.

Vancouver:

Campbell JC. IMPLEMENTATION OF A VERTICALLY INTEGRATED ICE SHEET MOMENTUM BALANCE MODEL. [Internet] [Masters thesis]. University of Montana; 2013. [cited 2021 Jan 26]. Available from: https://scholarworks.umt.edu/etd/552.

Council of Science Editors:

Campbell JC. IMPLEMENTATION OF A VERTICALLY INTEGRATED ICE SHEET MOMENTUM BALANCE MODEL. [Masters Thesis]. University of Montana; 2013. Available from: https://scholarworks.umt.edu/etd/552

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