Continental scale, high order, high spatial resolution, ice sheet modeling using the Ice Sheet System Model (ISSM)

Larour, Eric; Seroussi, Hélène; Morlighem, Mathieu; Rignot, Eric

doi:10.1029/2011jf002140

Cited by 458 publications

(608 citation statements)

References 98 publications

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“…Experiments are based on the MISMIP3D configurations. We use the Ice Sheet System Model (ISSM, Larour et al, 2012) to solve the 2-D shelfy-stream equations with spatial resolutions varying between 5 km and 250 m. We analyze the grounding line steady state position, its evolution following a perturbation in basal friction and the reversibility of its evolution for the different grounding line parameterizations. We conclude on the requirements needed to accurately capture grounding line motion and the impact of the underlying parameterization.…”

Section: H Seroussi Et Al: Grounding Line Parameterizationmentioning

confidence: 99%

Hydrostatic grounding line parameterization in ice sheet models

et al. 2014

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Abstract. Modeling of grounding line migration is essential to accurately simulate the behavior of marine ice sheets and investigate their stability. Here, we assess the sensitivity of numerical models to the parameterization of the grounding line position. We run the MISMIP3D benchmark experiments using the Ice Sheet System Model (ISSM) and a two-dimensional shelfy-stream approximation (SSA) model with different mesh resolutions and different sub-element parameterizations of grounding line position. Results show that different grounding line parameterizations lead to different steady state grounding line positions as well as different retreat/advance rates. Our simulations explain why some vertically depth-averaged model simulations deviate significantly from the vast majority of simulations based on SSA in the MISMIP3D benchmark. The results reveal that differences between simulations performed with and without sub-element parameterization are as large as those performed with different approximations of the stress balance equations in this configuration. They also demonstrate that the reversibility test is passed at relatively coarse resolution while much finer resolutions are needed to accurately capture the steady-state grounding line position. We conclude that fixed grid SSA models that do not employ such a parameterization should be avoided, as they do not provide accurate estimates of grounding line dynamics, even at high spatial resolution. For models that include sub-element grounding line parameterization, in the MISMIP3D configuration, a mesh resolution finer than 2 km should be employed.

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Section: H Seroussi Et Al: Grounding Line Parameterizationmentioning

confidence: 99%

Hydrostatic grounding line parameterization in ice sheet models

et al. 2014

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“…We refer to this model as our forward model. This model is implemented within the Ice Sheet System Model (Larour et al, 2012c;Morlighem et al, 2010). Here, we are interested in the best fit between modeled surface heights and available altimetry observations.…”

Section: Modelmentioning

confidence: 99%

“…We refer to Larour et al (2012c) for more details on the FEM discretization as well as numerical schemes to handle the material nonlinearity and the stability of our time stepping.…”

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confidence: 99%

Inferred basal friction and surface mass balance of the Northeast Greenland Ice Stream using data assimilation of ICESat (Ice Cloud and land Elevation Satellite) surface altimetry and ISSM (Ice Sheet System Model)

et al. 2014

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Abstract. We present a new data assimilation method within the Ice Sheet System Model (ISSM) framework that is capable of assimilating surface altimetry data from missions such as ICESat (Ice Cloud and land Elevation Satellite) into reconstructions of transient ice flow. The new method relies on algorithmic differentiation to compute gradients of objective functions with respect to model forcings. It is applied to the Northeast Greenland Ice Stream, where surface mass balance and basal friction forcings are temporally inverted, resulting in adjusted modeled surface heights that best fit existing altimetry. This new approach allows for a better quantification of basal and surface processes and a better understanding of the physical processes currently missing in transient ice-flow models to better capture the important intra-and interannual variability in surface altimetry. It also demonstrates that large spatial and temporal variability is required in model forcings such as surface mass balance and basal friction, variability that can only be explained by including more complex processes such as snowpack compaction at the surface and basal hydrology at the bottom of the ice sheet. This approach is indeed a first step towards assimilating the wealth of high spatial resolution altimetry data available from EnviSat, ICESat, Operation IceBridge and CryoSat-2, and that which will be available in the near future with the launch of ICESat-2.

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“…There is a whole hierarchy of approaches to solve this problem (see for instance the ISMIP inter-comparison project, Pattyn et al, 2008). Recently, a few ice sheet models were designed to solving rigorously the full Stokes problem, but given the numerical cost they are usually restricted to a regional scale or can only afford a few century simulations; see Gillet-Chaulet et al (2012), Larour et al (2012). All the other ice sheet models use approximations based on the very small aspect ratio of ice sheets.…”

Section: Basis Of Ice Sheet Modelmentioning

confidence: 99%

An ETKF approach for initial state and parameter estimation in ice sheet modelling

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Ritz

et al. 2014

Nonlin. Processes Geophys.

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Abstract. Estimating the contribution of Antarctica andGreenland to sea-level rise is a hot topic in glaciology. Good estimates rely on our ability to run a precisely calibrated ice sheet evolution model starting from a reliable initial state. Data assimilation aims to provide an answer to this problem by combining the model equations with observations. In this paper we aim to study a state-of-the-art ensemble Kalman filter (ETKF) to address this problem. This method is implemented and validated in the twin experiments framework for a shallow ice flowline model of ice dynamics. The results are very encouraging, as they show a good convergence of the ETKF (with localisation and inflation), even for small-sized ensembles.

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Continental scale, high order, high spatial resolution, ice sheet modeling using the Ice Sheet System Model (ISSM)

Cited by 458 publications

References 98 publications

Hydrostatic grounding line parameterization in ice sheet models

Hydrostatic grounding line parameterization in ice sheet models

Inferred basal friction and surface mass balance of the Northeast Greenland Ice Stream using data assimilation of ICESat (Ice Cloud and land Elevation Satellite) surface altimetry and ISSM (Ice Sheet System Model)

An ETKF approach for initial state and parameter estimation in ice sheet modelling

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