Ice Sheet Modeling: Accuracy of First-Order Stokes Model with Basal Sliding
Some climate models are still lacking features such as dynamical modelling of ice sheets due to their computational cost which results in poor accuracy and estimates of e.g. sea level rise. The need for low-cost high-order models initiated the development of the First-Order Stokes (or Blatter-Pattyn...
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Uppsala universitet, Institutionen för geovetenskaper
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ftuppsalauniv:oai:DiVA.org:uu-360245 2023-05-15T16:40:23+02:00 Ice Sheet Modeling: Accuracy of First-Order Stokes Model with Basal Sliding Istäckemodellering: Noggrannhet hos första ordningens Stokes modell med basalskjutning Jonsson, Eskil 2018 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-360245 eng eng Uppsala universitet, Institutionen för geovetenskaper Examensarbete vid Institutionen för geovetenskaper, 1650-6553 443 http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-360245 info:eu-repo/semantics/openAccess Ice sheet modelling First-Order Stokes model basal sliding Stokes equations Physical Geography Naturgeografi Student thesis info:eu-repo/semantics/bachelorThesis text 2018 ftuppsalauniv 2023-02-23T21:48:21Z Some climate models are still lacking features such as dynamical modelling of ice sheets due to their computational cost which results in poor accuracy and estimates of e.g. sea level rise. The need for low-cost high-order models initiated the development of the First-Order Stokes (or Blatter-Pattyn) model which retains much of the accuracy of the full-Stokes model but is also cost-effective. This model has proven accurate for ice sheets and glaciers with frozen bedrocks, or no-slip basal boundary conditions. However, experimental evidence seems to be lacking regarding its accuracy under sliding, or stress-free, bedrock conditions (ice-shelf conditions). Hence, it became of interest to investigate this. Numerical experiments were set up by formulating the first-order Stokes equations as a variational finite element problem, followed by implementing them using the open-source FEniCS framework. Two types of geometries were used with both no-slip and slip basal boundary conditions. Specifically, experiments B and D from the Ice Sheet Model Intercomparison Project for Higher-Order ice sheet Models (ISMIP-HOM) were used to benchmark the model. Local model errors were investigated and a convergence analysis was performed for both experiments. The results yielded an inherent model error of about 0.06% for ISMIP-HOM B and 0.006% for ISMIPHOM D, mostly relating to the different types of geometries used. Errors in stress-free regions were greater and varied on the order of 1%. This was deemed fairly accurate, and probably enough justification to replace models such as the Shallow Shelf Approximation with the First-Order Stokes model in some regions. However, more rigorous tests with real-world geometries may be warranted. Also noteworthy were inconsistent results in the vertical velocity under slippery conditions (ISMIPHOM D) which could either be due to coding errors or an inherent problem with the decoupling of the horizontal and vertical velocities of the First-Order Stokes model. This should be further investigated. ... Bachelor Thesis Ice Sheet Ice Shelf Uppsala University: Publications (DiVA) |
institution |
Open Polar |
collection |
Uppsala University: Publications (DiVA) |
op_collection_id |
ftuppsalauniv |
language |
English |
topic |
Ice sheet modelling First-Order Stokes model basal sliding Stokes equations Physical Geography Naturgeografi |
spellingShingle |
Ice sheet modelling First-Order Stokes model basal sliding Stokes equations Physical Geography Naturgeografi Jonsson, Eskil Ice Sheet Modeling: Accuracy of First-Order Stokes Model with Basal Sliding |
topic_facet |
Ice sheet modelling First-Order Stokes model basal sliding Stokes equations Physical Geography Naturgeografi |
description |
Some climate models are still lacking features such as dynamical modelling of ice sheets due to their computational cost which results in poor accuracy and estimates of e.g. sea level rise. The need for low-cost high-order models initiated the development of the First-Order Stokes (or Blatter-Pattyn) model which retains much of the accuracy of the full-Stokes model but is also cost-effective. This model has proven accurate for ice sheets and glaciers with frozen bedrocks, or no-slip basal boundary conditions. However, experimental evidence seems to be lacking regarding its accuracy under sliding, or stress-free, bedrock conditions (ice-shelf conditions). Hence, it became of interest to investigate this. Numerical experiments were set up by formulating the first-order Stokes equations as a variational finite element problem, followed by implementing them using the open-source FEniCS framework. Two types of geometries were used with both no-slip and slip basal boundary conditions. Specifically, experiments B and D from the Ice Sheet Model Intercomparison Project for Higher-Order ice sheet Models (ISMIP-HOM) were used to benchmark the model. Local model errors were investigated and a convergence analysis was performed for both experiments. The results yielded an inherent model error of about 0.06% for ISMIP-HOM B and 0.006% for ISMIPHOM D, mostly relating to the different types of geometries used. Errors in stress-free regions were greater and varied on the order of 1%. This was deemed fairly accurate, and probably enough justification to replace models such as the Shallow Shelf Approximation with the First-Order Stokes model in some regions. However, more rigorous tests with real-world geometries may be warranted. Also noteworthy were inconsistent results in the vertical velocity under slippery conditions (ISMIPHOM D) which could either be due to coding errors or an inherent problem with the decoupling of the horizontal and vertical velocities of the First-Order Stokes model. This should be further investigated. ... |
format |
Bachelor Thesis |
author |
Jonsson, Eskil |
author_facet |
Jonsson, Eskil |
author_sort |
Jonsson, Eskil |
title |
Ice Sheet Modeling: Accuracy of First-Order Stokes Model with Basal Sliding |
title_short |
Ice Sheet Modeling: Accuracy of First-Order Stokes Model with Basal Sliding |
title_full |
Ice Sheet Modeling: Accuracy of First-Order Stokes Model with Basal Sliding |
title_fullStr |
Ice Sheet Modeling: Accuracy of First-Order Stokes Model with Basal Sliding |
title_full_unstemmed |
Ice Sheet Modeling: Accuracy of First-Order Stokes Model with Basal Sliding |
title_sort |
ice sheet modeling: accuracy of first-order stokes model with basal sliding |
publisher |
Uppsala universitet, Institutionen för geovetenskaper |
publishDate |
2018 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-360245 |
genre |
Ice Sheet Ice Shelf |
genre_facet |
Ice Sheet Ice Shelf |
op_relation |
Examensarbete vid Institutionen för geovetenskaper, 1650-6553 443 http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-360245 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766030770379423744 |