Comparison of four calving laws to model Greenland outlet glaciers

Choi, Youngmin; Morlighem, Mathieu; Wood, Michael; Bondzio, Johannes H.

doi:10.5194/tc-2018-132

Cited by 12 publications

(22 citation statements)

References 23 publications

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“…Based on the above considerations, the von Mises and von Mises tensile stresses produce the most realistic calving front geometry evolutions for tidewater glaciers using a continuum damage mechanics model. This observation agrees with results from Choi et al (), who found that the von Mises tensile stress provides more satisfactory results than the three other calving laws in their comparison effort.…”

Section: Discussionsupporting

confidence: 92%

“…The presented model was implemented in plane‐strain formulation in a vertical section along the flow line. Consequently, important effects such as lateral stress bridging are neglected (Choi et al, ; Todd et al, ). The current model implementation is generic and can be used in three dimensions by only changing the finite element types to three‐dimensional hexahedral or tetrahedral elements.…”

Section: Discussionmentioning

confidence: 99%

“…This approach was used to model Store Gletscher's response to ocean thermal forcing. Further, Choi et al () compared four calving laws to determine calving front positions for several Greenland outlet glaciers. They found that the von Mises tensile stress calving law is best suited to simulate observed ice front positions.…”

Section: Introductionmentioning

confidence: 99%

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A Transient Coupled Ice Flow‐Damage Model to Simulate Iceberg Calving From Tidewater Outlet Glaciers

Mercenier

Lüthi

Vieli

2019

J Adv Model Earth Syst

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Iceberg calving, the detachment of an ice block at the glacier front, is the main process responsible for the dynamic mass loss from the ice sheets to the ocean. Understanding this process is essential to accurately predict ice sheet response to the future climate. We present a transient multiphysics finite-element model to simulate iceberg break-off and geometry evolution of a marine-terminating glacier. The model solves the coupled equations of ice flow, damage mechanics, oceanic melt, and geometry evolution on the same Lagrangian computational grid. A modeling sensitivity analysis shows that the choice of stress measure used for damage evolution strongly influences the resulting calving front geometries. Our analysis suggests that the von Mises stress measures produce the most realistic calving front geometry evolutions for tidewater glaciers. Submarine frontal melt is shown to have a strong impact on the calving front geometry. The presented multiphysics model includes all processes thus far shown to be relevant for the evolution of tidewater glaciers and can be readily adapted for 3-D and arbitrary bedrock geometries.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

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A Transient Coupled Ice Flow‐Damage Model to Simulate Iceberg Calving From Tidewater Outlet Glaciers

Mercenier

Lüthi

Vieli

2019

J Adv Model Earth Syst

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“…Shorter periods are more prone to noisy results, but offer higher temporal resolution, while an increase in temporal integration time smoothens the results. to the operational products) which affects observational constraints for models of flow dynamics of calving and our understanding of terminus dynamics (Nick et al, 2009Choi et al, 2018;Morlighem et al, 2017;King et al, 2018).…”

Section: Comparison To Operational Ice Velocity Productsmentioning

confidence: 99%

Multisensor validation of tidewater glacier flow fields derived from SAR intensity tracking

Rohner

Small

Henke

et al. 2019

Preprint

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Following the general warming trend in Greenland, an increase in calving rates, retreat and ice flow has been observed at ocean-terminating outlet glaciers. These changes contribute substantially to the current mass loss of the Greenland Ice Sheet. In order to constrain models of ice dynamics as well as estimates of mass change, detailed knowledge of geometry and ice-flow are needed, in particular on the rapidly changing tongues of ocean-terminating outlet glaciers. In this study, we validate velocity estimates and spatial patterns close to the calving terminus of such an outlet derived from an iterative offset 5 tracking method based on SAR intensity data with a collection of three independent reference measurements of glacier flow.These reference data sets are comprised of measurements from differential GPS, a Terrestrial Radar Interferometer (TRI) and repeated UAV surveys. Our approach for the SAR-velocity processing aims achieving at high spatial and temporal resolution in order to best resolve the steep velocity gradients in the terminus area and to exploit the 12 day repeat interval of the singlesatellite Sentinel-1A sensor. Results from images of the medium-sized ocean terminating outlet glacier Eqip Sermia acquired by 10 Sentinel-1A and RADARSAT-2 exhibit a mean difference of 8.7% when compared to the corresponding GPS measurements.An areal comparison of our SAR velocity-fields with independently generated velocity maps from TRI and UAV showed a good agreement in magnitude and spatial patterns, with mean differences smaller than 0.7 m·d -1 . In comparison with existing operational velocity products, our SAR-derived velocities showed a strongly improved spatial velocity pattern near the margins and calving front. There 10% to 20% higher surface ice velocities are produced, which has substantial implications on ice fluxes 15 and on mass budget estimates of ice sheets. Further, we showed that offset tracking from SAR intensity data at a high spatiotemporal resolution is a valid method to derive glacier flow fields for fast-flowing glacier termini of outlet glaciers and, given the repeat interval of 12 days of the Sentinel-1A sensor (6 days with Sentinel-1B), has the potential to be applied operationally in a quasi-continuous mode.

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“…First, there is still debate on how to parameterize important processes like submarine terminus melt, calving, and basal sliding. The recent surge of new observational data around the GrIS has enabled observation‐based testing of a number of existing process parameterizations that control glacier flow (Bondzio et al, ; Choi et al, ; Choi et al, ; Enderlin & Bartholomaus, ; Stearns & van der Veen, ), but these must be generalized across all glacier systems and validated with observations. Second, improvements in model resolution and nested modeling techniques are beginning to allow full ice sheet models to resolve outlet glaciers (Aschwanden et al, ; Aschwanden et al, ), but resolution challenges continue.…”

Section: Future Research Needsmentioning

confidence: 99%

Future Evolution of Greenland's Marine‐Terminating Outlet Glaciers

et al. 2020

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Mass loss from the Greenland ice sheet (GrIS) has increased over the last two decades in response to changes in global climate, motivating the scientific community to question how the GrIS will contribute to sea‐level rise on timescales that are relevant to coastal communities. Observations also indicate that the impact of a melting GrIS extends beyond sea‐level rise, including changes to ocean properties and circulation, nutrient and sediment cycling, and ecosystem function. Unfortunately, despite the rapid growth of interest in GrIS mass loss and its impacts, we still lack the ability to confidently predict the rate of future mass loss and the full impacts of this mass loss on the globe. Uncertainty in GrIS mass loss projections in part stems from the nonlinear response of the ice sheet to climate forcing, with many processes at play that influence how mass is lost. This is particularly true for outlet glaciers in Greenland that terminate in the ocean because their flow is strongly controlled by multiple processes that alter their boundary conditions at the ice‐atmosphere, ice‐ocean, and ice‐bed interfaces. Many of these processes change on a range of overlapping timescales and are challenging to observe, making them difficult to understand and thus missing in prognostic ice sheet/climate models. For example, recent (beginning in the late 1990s) mass loss via outlet glaciers has been attributed primarily to changing ice‐ocean interactions, driven by both oceanic and atmospheric warming, but the exact mechanisms controlling the onset of glacier retreat and the processes that regulate the amount of retreat remain uncertain. Here we review the progress in understanding GrIS outlet glacier sensitivity to climate change, how mass loss has changed over time, and how our understanding has evolved as observational capacity expanded. Although many processes are far better understood than they were even a decade ago, fundamental gaps in our understanding of certain processes remain. These gaps impede our ability to understand past changes in dynamics and to make more accurate mass loss projections under future climate change. As such, there is a pressing need for (1) improved, long‐term observations at the ice‐ocean and ice‐bed boundaries, (2) more observationally constrained numerical ice flow models that are coupled to atmosphere and ocean models, and (3) continued development of a collaborative and interdisciplinary scientific community.

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Comparison of four calving laws to model Greenland outlet glaciers

Cited by 12 publications

References 23 publications

A Transient Coupled Ice Flow‐Damage Model to Simulate Iceberg Calving From Tidewater Outlet Glaciers

A Transient Coupled Ice Flow‐Damage Model to Simulate Iceberg Calving From Tidewater Outlet Glaciers

Multisensor validation of tidewater glacier flow fields derived from SAR intensity tracking

Future Evolution of Greenland's Marine‐Terminating Outlet Glaciers

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