Neutral equilibrium and forcing feedbacks in marine ice sheet modelling
Poor convergence with resolution of ice sheet models when simulating grounding line migration has been known about for over a decade. However, some of the associated numerical artefacts remain absent from the published literature. In the current study we apply a Stokes-flow finite-element marine ice...
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fttriple:oai:gotriple.eu:oai:doaj.org/article:501efe1ebdeb430499049e0c287e3906 2023-05-15T16:40:23+02:00 Neutral equilibrium and forcing feedbacks in marine ice sheet modelling R. M. Gladstone Y. Xia J. Moore 2018-11-01 https://doi.org/10.5194/tc-12-3605-2018 https://www.the-cryosphere.net/12/3605/2018/tc-12-3605-2018.pdf https://doaj.org/article/501efe1ebdeb430499049e0c287e3906 en eng Copernicus Publications doi:10.5194/tc-12-3605-2018 1994-0416 1994-0424 https://www.the-cryosphere.net/12/3605/2018/tc-12-3605-2018.pdf https://doaj.org/article/501efe1ebdeb430499049e0c287e3906 undefined The Cryosphere, Vol 12, Pp 3605-3615 (2018) geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2018 fttriple https://doi.org/10.5194/tc-12-3605-2018 2023-01-22T19:25:28Z Poor convergence with resolution of ice sheet models when simulating grounding line migration has been known about for over a decade. However, some of the associated numerical artefacts remain absent from the published literature. In the current study we apply a Stokes-flow finite-element marine ice sheet model to idealised grounding line evolution experiments. We show that with insufficiently fine model resolution, a region containing multiple steady-state grounding line positions exists, with one steady state per node of the model mesh. This has important implications for the design of perturbation experiments used to test convergence of grounding line behaviour with resolution. Specifically, the design of perturbation experiments can be under-constrained, potentially leading to a “false positive” result. In this context a false positive is an experiment that appears to achieve convergence when in fact the model configuration is not close to its converged state. We demonstrate a false positive: an apparently successful perturbation experiment (i.e. reversibility is shown) for a model configuration that is not close to a converged solution. If perturbation experiments are to be used in the future, experiment design should be modified to provide additional constraints to the initialisation and spin-up requirements. This region of multiple locally stable steady-state grounding line positions has previously been mistakenly described as neutral equilibrium. This distinction has important implications for understanding the impacts of discretising a forcing feedback involving grounding line position and basal friction. This forcing feedback cannot, in general, exist in a region of neutral equilibrium and could be the main cause of poor convergence in grounding line modelling. Article in Journal/Newspaper Ice Sheet The Cryosphere Unknown The Cryosphere 12 11 3605 3615 |
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geo envir R. M. Gladstone Y. Xia J. Moore Neutral equilibrium and forcing feedbacks in marine ice sheet modelling |
topic_facet |
geo envir |
description |
Poor convergence with resolution of ice sheet models when simulating grounding line migration has been known about for over a decade. However, some of the associated numerical artefacts remain absent from the published literature. In the current study we apply a Stokes-flow finite-element marine ice sheet model to idealised grounding line evolution experiments. We show that with insufficiently fine model resolution, a region containing multiple steady-state grounding line positions exists, with one steady state per node of the model mesh. This has important implications for the design of perturbation experiments used to test convergence of grounding line behaviour with resolution. Specifically, the design of perturbation experiments can be under-constrained, potentially leading to a “false positive” result. In this context a false positive is an experiment that appears to achieve convergence when in fact the model configuration is not close to its converged state. We demonstrate a false positive: an apparently successful perturbation experiment (i.e. reversibility is shown) for a model configuration that is not close to a converged solution. If perturbation experiments are to be used in the future, experiment design should be modified to provide additional constraints to the initialisation and spin-up requirements. This region of multiple locally stable steady-state grounding line positions has previously been mistakenly described as neutral equilibrium. This distinction has important implications for understanding the impacts of discretising a forcing feedback involving grounding line position and basal friction. This forcing feedback cannot, in general, exist in a region of neutral equilibrium and could be the main cause of poor convergence in grounding line modelling. |
format |
Article in Journal/Newspaper |
author |
R. M. Gladstone Y. Xia J. Moore |
author_facet |
R. M. Gladstone Y. Xia J. Moore |
author_sort |
R. M. Gladstone |
title |
Neutral equilibrium and forcing feedbacks in marine ice sheet modelling |
title_short |
Neutral equilibrium and forcing feedbacks in marine ice sheet modelling |
title_full |
Neutral equilibrium and forcing feedbacks in marine ice sheet modelling |
title_fullStr |
Neutral equilibrium and forcing feedbacks in marine ice sheet modelling |
title_full_unstemmed |
Neutral equilibrium and forcing feedbacks in marine ice sheet modelling |
title_sort |
neutral equilibrium and forcing feedbacks in marine ice sheet modelling |
publisher |
Copernicus Publications |
publishDate |
2018 |
url |
https://doi.org/10.5194/tc-12-3605-2018 https://www.the-cryosphere.net/12/3605/2018/tc-12-3605-2018.pdf https://doaj.org/article/501efe1ebdeb430499049e0c287e3906 |
genre |
Ice Sheet The Cryosphere |
genre_facet |
Ice Sheet The Cryosphere |
op_source |
The Cryosphere, Vol 12, Pp 3605-3615 (2018) |
op_relation |
doi:10.5194/tc-12-3605-2018 1994-0416 1994-0424 https://www.the-cryosphere.net/12/3605/2018/tc-12-3605-2018.pdf https://doaj.org/article/501efe1ebdeb430499049e0c287e3906 |
op_rights |
undefined |
op_doi |
https://doi.org/10.5194/tc-12-3605-2018 |
container_title |
The Cryosphere |
container_volume |
12 |
container_issue |
11 |
container_start_page |
3605 |
op_container_end_page |
3615 |
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1766030784952532992 |