Assessing the ability of numerical ice sheet models to simulate grounding line migration

Vieli, Andreas

doi:10.1029/2004jf000202

Cited by 175 publications

(295 citation statements)

References 37 publications

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“…Although buttressing effects can be included in a parameterized way (Vieli and Payne 2005;Pattyn et al 2006), real three-dimensional effects are lacking. A number of three-dimensional models that cope with grounding line migration in a verified way have been developed or are in the process of development (Pollard and DeConto 2009;Goldberg et al 2009;Robison et al 2009;Katz and Worster 2010), where the Pollard and DeConto model incorporates the heuristic rule as in the above experiments.…”

Section: Discussion and Outlookmentioning

confidence: 99%

“…Large grid sizes, for instance, prevent grounding line migration. Only small enough grid sizes lead to grounding line advance (Huybrechts et al 1998;Vieli and Payne 2005;Durand et al 2009b). To test the grid size sensitivity, we carried out model experiments with different grid sizes, i.e.…”

Section: Methodsmentioning

confidence: 99%

“…Models that are either non-staggered or do not include the boundary condition converge only to the same advance-retreat position for sufficiently small grid sizes, which is considered a deficiency of fixed grid finite-difference models (Vieli and Payne 2005;Durand et al 2009b;Gladstone et al 2010). Results also depend on model type, i.e.…”

Section: Downward-sloping Bedmentioning

confidence: 99%

“…the grounding line coincides exactly with a grid point (Hindmarsh 1996;Hindmarsh and Le Meur 2001). Vieli and Payne (2005) showed that there is a strong dependency of FG models on numerics, that-when perturbed-FG models exhibit large changes in grounding line migration, and that these changes are irreversible. Conversely, for MG models, changes in grounding line position are generally small and reversible.…”

Section: Numerical Approachesmentioning

confidence: 99%

“…Conversely, for MG models, changes in grounding line position are generally small and reversible. However, the models based on shallow-ice approximation used by Vieli and Payne lack a second independent boundary condition that is needed to accurately represent grounding line migration (see below ;Schoof 2007a;Durand et al 2009a), and although MG models generally produce more consistent results, a major drawback remains the complexity to implement in a threedimensional ice sheet model (Vieli and Payne 2005).…”

Section: Numerical Approachesmentioning

confidence: 99%

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Representing Grounding Line Dynamics in Numerical Ice Sheet Models: Recent Advances and Outlook

Docquier¹,

Perichon²,

Pattyn³

2011

The Earth's Cryosphere and Sea Level Change

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Recent satellite observations of the Antarctic and Greenland ice sheets show accelerated ice flow and associated ice sheet thinning along coastal outlet glaciers in contact with the ocean. Both processes are the result of grounding line retreat due to melting at the grounding line (the grounding line is the contact of the ice sheet with the ocean, where it starts to float and forms an ice shelf or ice tongue). Such rapid ice loss is not yet included in large-scale ice sheet models used for IPCC projections, as most of the complex processes are poorly understood. Here we report on the state-of-the art of grounding line migration in marine ice sheets and address different ways in which grounding line migration can be attributed and represented in ice sheet models. Using onedimensional ice flow models of the ice sheet/ice shelf system we carried out a number of sensitivity experiments with different spatial resolutions and stress approximations. These are verified with semi-analytical steady state solutions. Results show that, in large-scale finite-difference models, grounding line migration is dependent on the numerical treatment (e.g. staggered/non-staggered grid) and the level of physics involved (e.g. shallow-ice/ shallow-shelf approximation).

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Section: Discussion and Outlookmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Downward-sloping Bedmentioning

confidence: 99%

Section: Numerical Approachesmentioning

confidence: 99%

Section: Numerical Approachesmentioning

confidence: 99%

See 3 more Smart Citations

Representing Grounding Line Dynamics in Numerical Ice Sheet Models: Recent Advances and Outlook

Docquier¹,

Perichon²,

Pattyn³

2011

The Earth's Cryosphere and Sea Level Change

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Understanding controls on rapid ice‐stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model

et al. 2014

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[1] Using a one-dimensional numerical model of ice-stream flow with robust grounding-line dynamics, we explore controls on paleo-ice-stream retreat in Marguerite Bay, Antarctica, during the last deglaciation. Landforms on the continental shelf constrain the numerical model and suggest that retreat was rapid but punctuated by a series of slowdowns. We investigate the sensitivity of ice-stream retreat to changes in subglacial and lateral topography and to forcing processes including sea-level rise, enhanced melting beneath an ice shelf, atmospheric warming, and ice-shelf debuttressing. Our experiments consistently reproduce punctuated retreat on a bed that deepens inland, with retreat-rate slowdowns controlled by narrowings in the topography. Sensitivity experiments indicate that the magnitudes of change required for individual forcing mechanisms to initiate retreat are unrealistically high but that thresholds are reduced when processes act in combination. The ice stream is, however, most sensitive to ocean warming and associated ice-shelf melting, and retreat was most likely in response to external forcing that endured throughout the period of retreat rather than to a single triggering "event." Timescales of retreat are further controlled by the delivery of ice from upstream of the grounding line. Due to the influence of topography, modeled retreat patterns are insensitive to the temporal pattern of forcing evolution. We therefore suggest that despite regionally similar forcing mechanisms, landscape controls significant contrasts in retreat behavior between adjacent but topographically distinct catchments. Patterns of ice-stream retreat in the past, present, and future should therefore be expected to vary significantly.

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Rapid grounding line migration induced by internal ice stream variability

2014

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Observations indicate that the grounding line position of West Antarctica is sensitive to both forced and unforced ice stream variabilities. This study endeavors to characterize and understand unforced ice stream variability and associated grounding line migration. We use a flowline ice stream model with an undrained plastic bed, lateral shear stresses, and a stretched grid refined in the grounding zone. This model exhibits parameter space structure and hysteresis behavior similar to simpler ice stream models. Low prescribed temperature at the ice surface or weak geothermal heating produces thermal oscillations between active and stagnant phases. As in previous spatially resolved ice flow models, thermal activation propagates as an “activation wave.” This model's fine resolution of the grounding zone allows for accurate simulations of transient, unforced grounding line migration. Upstream of the grounding zone, horizontal grid spacing of 1 km is required to accurately resolve activation waves. Activation waves induce the grounding line to migrate over 100 km at a rate that can exceed 1 km/yr. This is followed during the active phase by retreat, which then continues for the duration of the stagnant phase. Grounding line retreat is the result of a negative mass balance near the grounding line but is not necessarily associated with negative mass balance for the entire ice stream in our simulations of internal variability. The novel approach and experiments described in this study show that there can be large excursions in grounding line position in the absence of either external forcing or retrograde slopes.

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Assessing the ability of numerical ice sheet models to simulate grounding line migration

Cited by 175 publications

References 37 publications

Representing Grounding Line Dynamics in Numerical Ice Sheet Models: Recent Advances and Outlook

Representing Grounding Line Dynamics in Numerical Ice Sheet Models: Recent Advances and Outlook

Understanding controls on rapid ice‐stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model

Rapid grounding line migration induced by internal ice stream variability

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