Numerical ice sheet modeling is a rather young discipline: it started in the 1950s. The "first generation" models developed at that time are currently being replaced by "new generations" ones, such as e.g. ARCTIC-TARAH. ARCTIC-TARAH is a Bert Bolin Center for Climate Research spin-off from the Pennsylvania State University Ice sheet model (PSUI). When the Bolin Center received PSUI for subsequent independent development and adaption of the code to Arctic settings in 2010, an initial inspection of the source code suggested that PSUI also contained a module that allows for the treatment of glacial hydraulics. A numerical ice sheet model including coupling of ice dynamics and hydraulics is an extremely important tool in testing new hypotheses of former geological events. E.g., based on the recent finding that Arctic Ocean sediments contain a very distinct signature, it has been suggested that ice dammed lakes at the south-eastern margin of the late Weichselian Eurasian ice sheet drained into the Arctic Ocean in a catastrophic event around 55.000 years ago. The aim of this thesis is to perform a reconnaissance analysis of the glacio-hydraulic algorithms in ARCTIC-TARAH, as "inherited" (but never with published record of functionality) from PSUI. The work is carried out in two steps: first the routines and algorithms describing the hydraulics are located and explored, and then these routines are tested and verified by performing experiment simulations. The investigation of the program code reveals the presence of two hydraulics related modules in ARCTIC-TARAH. The main tasks of the module Water are to initiate lakes and oceans and to adjust hydrostatic pressure in each lake. Further, with the module Move Water activated, transportation of water (e.g. in rivers) is possible. Results from idealized experiment simulations verify the functionality of the routines in the module Water. An in-depth analysis of the module Move Water suggests that there is a mismatch in time units when solving the equations describing flow of water. Experiment simulations also support this flaw detected in the flow model. Preliminary adjustments were made to the source code of the module Move Water, which made it possible to simulate the transportation of water both under an ice sheet and in rivers on land. However, these adjustments do not solve the problem of mismatching time scales, and the numerical solutions obtained from the experiments were observed to be unstable and, therefore, possibly incorrect. To be able to perform more advanced simulations in support of the above mentioned hypothesis, the flow model in the module Move Water needs to be improved or replaced. One solution to the problem with mismatching time scales, could be to use a so called multiscale solution in time.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-179861 |
| Date | January 2012 |
| Creators | Holmgren, Hanna |
| Publisher | Uppsala universitet, Institutionen för informationsteknologi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | UPTEC F, 1401-5757 ; 12029 |
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