Supplementary material to "Numerical issues in modeling ice sheet instabilities such as binge-purge type cyclic ice stream surging"

Hank, Kevin; Tarasov, Lev; Mantelli, Elisa

doi:10.5194/egusphere-2023-81-supplement

Cited by 3 publications

(9 citation statements)

References 1 publication

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“…Instructions on how to install and run PISM and the PISM source code (v2.0.2) can be acquired from the repository at https://zenodo.org/record/6001196. Further information on how to recreate this work's results, input files, parameter vectors, and the analysis scripts used to determine the surge characteristcs can be found at https://doi.org/10.5281/zenodo.7668490 (Hank, 2023). the GSM.…”

Section: Discussionmentioning

confidence: 99%

“…The surge propagates nearly symmetrically until the pseudo-Hudson Bay area is reached (t = 6.77 kyr in Fig. 3 and video 02 of Hank (2023)). After this point, the northern branch of the ice stream propagates more rapidly and extends further to the West than the southern branch.…”

Section: Surge Onset Propagation and Terminationmentioning

confidence: 95%

“…At t = 6.69 kyr, the SSA is activated (Sec. 2.1.1), and the longitudinal stress gradient and horizontal shear terms provide additional heating (heating due to shelfy stream dynamics in video 01 of Hank (2023)).…”

Section: Surge Onset Propagation and Terminationmentioning

confidence: 99%

“…Depending on the location of the adjacent minimum grid cell center basal temperature, either the ice flow (when the adjacent minimum basal temperature is downstream) or upstream propagation of the surge should be affected. For the large-scale surges, the adjacent minimum basal temperature is almost exclusively located upstream (e.g., video 02 of Hank (2023)). Changing the weight, therefore, affects the surge propagation rather than blocking parts of the ice flow.…”

Section: Weight Of Adjacent Minimum Basal Temperaturementioning

confidence: 99%

“…Changing the basal temperature ramp can somewhat counteract this discrepancy by enabling basal sliding at lower basal temperatures for coarser grid resolutions (Fig. 8 and video 05 of Hank (2023)). Further details on discrepancies between horizontal grid resolutions for individual parameter vectors are discussed in Sec.…”

Section: Gsm Convergence Study Without Basal Hydrologymentioning

confidence: 99%

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Numerical issues in modeling ice sheet instabilities such as binge-purge type cyclic ice stream surging

Hank

Tarasov

Mantelli

2023

Preprint

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Abstract. As in any environmental system, modeling instabilities within the glacial system is a numerical challenge of potentially high real-world relevance. Differentiating between the impacts of physical system processes and numerical noise is not straightforward. Here we use an idealized North American geometry and climate representation (similar to the HEINO experiments, Calov et al., 2010) to examine the numerical sensitivity of ice stream surge cycling in glaciological models. Through sensitivity tests, we identify some numerical requirements for a robust model configuration for such contexts. To partly address model-specific dependencies, we use both the Glacial Systems Model (GSM) and Parallel Ice Sheet Model (PISM). We show that modeled surge characteristics are resolution-dependent though converging (decreasing differences between resolutions) at higher horizontal grid resolutions. Discrepancies between high and coarse horizontal grid resolutions can be reduced by incorporating a resolution-dependent basal temperature ramp for basal sliding thermal activation. Inclusion of a diffusive bed thermal model reduces the surge cycling ice volume change by ∼33 % as the additional heat storage dampens the change in basal temperature during surge events. The inclusion of basal hydrology, as well as a non-flat topography, leads to increased ice volume change during surge events (∼20 and 17 %, respectively). Therefore, these latter three components are essential if one is endeavoring to maximize physical fidelity in ice stream surge cycle modeling. An abrupt transition between hard bedrock and soft sediment, as in the HEINO experiments, leads to ice stream propagation along this boundary but is not the cause of the main surge events.

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Section: Discussionmentioning

confidence: 99%

Section: Surge Onset Propagation and Terminationmentioning

confidence: 95%

Section: Surge Onset Propagation and Terminationmentioning

confidence: 99%

Section: Weight Of Adjacent Minimum Basal Temperaturementioning

confidence: 99%

Section: Gsm Convergence Study Without Basal Hydrologymentioning

confidence: 99%

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Numerical issues in modeling ice sheet instabilities such as binge-purge type cyclic ice stream surging

Hank

Tarasov

Mantelli

2023

Preprint

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Supplementary material to "Numerical issues in modeling ice sheet instabilities such as binge-purge type cyclic ice stream surging"

Hank¹,

Tarasov²,

Mantelli³

2023

Preprint

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The comparative role of physical system processes in Hudson Strait ice stream cycling: a comprehensive model-based test of Heinrich event hypotheses

Hank,

Tarasov

2024

Preprint

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Abstract. Despite their recognized significance on global climate and extensive research efforts, the mechanism(s) driving Heinrich Events remain(s) a subject of debate. Here, we use the 3D thermo-mechanically coupled Glacial Systems Model (GSM) to examine Hudson Strait ice stream surge cycling as well as the role of 3 factors previously hypothesized to play a critical role in Heinrich events: ice shelves, glacial isostatic adjustment, and sub-surface ocean temperature forcings. In contrast to all previous modeling studies examining HEs, the GSM uses a transient last glacial cycle climate forcing, global visco-elastic glacial isostatic adjustment model, and sub-glacial hydrology model. The results presented here are based on a high-variance sub-ensemble retrieved from North American history matching for the last glacial cycle. Over our comparatively wide sampling of the potential parameter space (52 ensemble parameters for climate forcing and process uncertainties), we find two modes of Hudson Strait ice streaming: classic binge-purge versus near continuous ice streaming with occasional shutdowns and subsequent surge onset overshoot. Our model results indicate that large ice shelves covering the Labrador Sea during the last glacial cycle only occur when extreme calving restrictions are applied. The otherwise minor ice shelves provide insignificant buttressing for the Hudson Strait ice stream. While sub-surface ocean temperature forcing leads to minor differences regarding surge characteristics, glacial isostatic adjustment does have a significant impact. Given input uncertainties, the strongest controls on ice stream surge cycling are the poorly constrained deep geothermal heat flux under Hudson Bay and Hudson Strait and the basal drag law. Decreasing the geothermal heat flux within available constraints and/or using a Coulomb sliding law instead of a Weertman-type power law leads to a shift from the near-continuous streaming mode to the binge-purge mode.

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Supplementary material to "Numerical issues in modeling ice sheet instabilities such as binge-purge type cyclic ice stream surging"

Cited by 3 publications

References 1 publication

Numerical issues in modeling ice sheet instabilities such as binge-purge type cyclic ice stream surging

Numerical issues in modeling ice sheet instabilities such as binge-purge type cyclic ice stream surging

Supplementary material to "Numerical issues in modeling ice sheet instabilities such as binge-purge type cyclic ice stream surging"

The comparative role of physical system processes in Hudson Strait ice stream cycling: a comprehensive model-based test of Heinrich event hypotheses

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