Ice shelf fracture parameterization in an ice sheet model

Sun, Sainan; Cornford, Stephen; Moore, John C.; Gladstone, Rupert; Zhao, Liyun

doi:10.5194/tc-11-2543-2017

Cited by 37 publications

(50 citation statements)

References 44 publications

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“…5) is computed from biased-corrected CMIP5 model projections up to 2300 from the model selection presented in Schannwell et al (2015). The bias correction and melt computation approach follow Trusel et al (2015). In brief, December-January-February (DJF) near-surface temperatures from the CMIP5 historical simulations were compared to high-resolution (5.5 km) RACMO2.3 simulations (van Wessem et al, 2016) such that…”

Section: Calvingmentioning

confidence: 99%

Dynamic response of Antarctic Peninsula Ice Sheet to potential collapse of Larsen C and George VI ice shelves

et al. 2018

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Abstract. Ice shelf break-up and disintegration events over the past 5 decades have led to speed-up, thinning, and retreat of upstream tributary glaciers and increases to rates of global sea-level rise. The southward progression of these episodes indicates a climatic cause and in turn suggests that the larger Larsen C and George VI ice shelves may undergo a similar collapse in the future. However, the extent to which removal of the Larsen C and George VI ice shelves will affect upstream tributary glaciers and add to global sea levels is unknown. Here we apply numerical ice-sheet models of varying complexity to show that the centennial sea-level commitment of Larsen C embayment glaciers following immediate shelf collapse is low (<2.5 mm to 2100, <4.2 mm to 2300). Despite its large size, Larsen C does not provide strong buttressing forces to upstream basins and its collapse does not result in large additional discharge from its tributary glaciers in any of our model scenarios. In contrast, the response of inland glaciers to a collapse of the George VI Ice Shelf may add up to 8 mm to global sea levels by 2100 and 22 mm by 2300 due in part to the mechanism of marine ice sheet instability. Our results demonstrate the varying and relative importance to sea level of the large Antarctic Peninsula ice shelves considered to present a risk of collapse.

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Section: Calvingmentioning

confidence: 99%

Dynamic response of Antarctic Peninsula Ice Sheet to potential collapse of Larsen C and George VI ice shelves

et al. 2018

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“…It is useful to compare our results to those of Dansereau et al () and Sun et al (). Dansereau et al developed a sea ice model based on the so‐called Maxwell viscoelastic model, which includes both fracture and healing.…”

Section: Discussionmentioning

confidence: 76%

“…It is useful to compare our results to those of Dansereau et al (2016) and Sun et al (2017). Dansereau .…”

Section: Discussionmentioning

confidence: 99%

Effective Rheology Across the Fragmentation Transition for Sea Ice and Ice Shelves

Åström

Benn

2019

Geophysical Research Letters

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Sea ice and ice shelves can be described by a viscoelastic rheology that is approximately linear elastic and brittle at high strain rates and viscously shear thinning at low strain rates. Brittle ice easily fractures under compressive shear and forms shear bands as the material undergoes a transition to a fragmented, granular state. This transition plays a central role in the mechanical behavior at large scales of sea ice in the Arctic Ocean or Antarctic ice shelves. Here we demonstrate that the fragmentation transition is characterized by an essentially discontinuous drop of three to five orders of magnitude in effective viscosity and stress relaxation time. Beyond the fragmentation transition, grinding in shear zones further reduces both effective viscosity and shear stiffness, but with an essentially constant relaxation time of ∼10 s. These results are relevant for ice rheology implementation in large‐scale climate‐related models of sea ice and thin ice shelves.

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“…Our assumption of simple Weertman basal drag (Eq. 7) may be improved by implementing a physics-based basal sliding law (Schoof and Hindmarsh, 2010;Gagliardini et al, 2014;Tsai et al, 2015), although basal drag accounts for only about 2% of present-day buttressing (Shapero et al, 2016). An improved sliding relation would likely produce more speedup and retreat in model results as dynamic thinning can reduce the effective pressure, leading to lower basal shear stress.…”

Section: Model Improvementsmentioning

confidence: 99%

“…Several sliding parameterizations (also termed sliding relations or sliding laws) have been used in the literature that assume basal drag depends on sliding speed (so-called Weertman sliding; Weertman, 1957) or on effective pressure (Schoof and Hindmarsh, 2010;Gagliardini et al, 2014). Tsai et al (2015) introduced a combined Weertman and Coulomb sliding law based on effective pressures with a boundary layer at the grounding line; this has a higher scaling of ice flux with grounding line thickness compared with the Weertman sliding. However, in the Jakobshavn case, both Weertman and Coulomb sliding produce very similar fluxes because the basal shear stresses along the main trough are typically only 2 % of the driving force (Shapero et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Simulated retreat of Jakobshavn Isbræ during the 21st century

et al. 2019

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The early 21st century retreat of Jakobshavn Isbrae into its overdeepened bedrock trough was accompanied by acceleration to unprecedented ice stream speeds. Such dramatic changes suggested the possibility of substantial mass loss over the rest of this century. Here we use a threedimensional ice sheet model with parameterizations to represent the effects of ice mélange buttressing, crevasse-depthbased calving and submarine melting to adequately reproduce its recent evolution. We are the first study on Jakobshavn Isbrae that solves for three-dimensional ice flow coupled with representations of hydro-fracturing-induced calving and mélange buttressing. Additionally, the model can accurately replicate interannual variations in grounding line and terminus position, including seasonal fluctuations that emerged after arriving at the overdeepened basin and the disappearance of its floating ice shelf. Our simulated ice viscosity variability due to shear margin evolution is particularly important in reproducing the large observed interannual changes in terminus velocity. We use this model to project Jakobshavn's evolution over this century, forced by ocean temperatures from seven Earth system models and surface runoff derived from RACMO, all under the IPCC RCP4.5 climate scenario. In our simulations, Jakobshavn's grounding line continues to retreat ∼ 18.5 km by the end of this century, leading to a total mass loss of ∼ 2068 Gt (5.7 mm sea level rise equivalent). Despite the relative success of the model in simulating the recent behavior of the glacier, the model does not simulate winter calving events that have become relatively more important.Published by Copernicus Publications on behalf of the European Geosciences Union.

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Ice shelf fracture parameterization in an ice sheet model

Cited by 37 publications

References 44 publications

Dynamic response of Antarctic Peninsula Ice Sheet to potential collapse of Larsen C and George VI ice shelves

Dynamic response of Antarctic Peninsula Ice Sheet to potential collapse of Larsen C and George VI ice shelves

Effective Rheology Across the Fragmentation Transition for Sea Ice and Ice Shelves

Simulated retreat of Jakobshavn Isbræ during the 21st century

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