A Simple Law for Ice-Shelf Calving

Alley, Richard B.; Horgan, Huw; Joughin, Ian; Cuffey, Kurt M.; Dupont, T. K.; Parizek, B. R.; Anandakrishnan, S.; Bassis, J. N.

doi:10.1126/science.1162543

Cited by 95 publications

(117 citation statements)

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“…At present and pending further development, ISSM is already capable of tackling systems of several [78] Several modules are currently being developed to improve ISSM. One module will include a calving law to constrain ice front positions and their time evolution, following the work of Alley et al [2008], Walter et al [2010], and Bassis [2011]. Second, we will include a more sophisticated, higher-order scheme of grounding line dynamics as by Nowicki [2007] to capture ice flow instabilities, nonlinearities and hysteretic effects, which may not be well captured with our current hydrostatic criterion.…”

Section: Discussionmentioning

confidence: 99%

Dynamically and Observationally Constrained Estimates of Water-Mass Distributions and Ages in the Global Ocean

DeVries

Primeau

2011

Journal of Physical Oceanography

180

202

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[1] Ice flow models used to project the mass balance of ice sheets in Greenland and Antarctica usually rely on the Shallow Ice Approximation (SIA) and the Shallow-Shelf Approximation (SSA), sometimes combined into so-called "hybrid" models. Such models, while computationally efficient, are based on a simplified set of physical assumptions about the mechanical regime of the ice flow, which does not uniformly apply everywhere on the ice sheet/ice shelf system, especially near grounding lines, where rapid changes are taking place at present. Here, we present a new thermomechanical finite element model of ice flow named ISSM (Ice Sheet System Model) that includes higher-order stresses, high spatial resolution capability and data assimilation techniques to better capture ice dynamics and produce realistic simulations of ice sheet flow at the continental scale. ISSM includes several approximations of the momentum balance equations, ranging from the two-dimensional SSA to the three-dimensional full-Stokes formulation. It also relies on a massively parallelized architecture and state-of-the-art scalable tools. ISSM employs data assimilation techniques, at all levels of approximation of the momentum balance equations, to infer basal drag at the ice-bed interface from satellite radar interferometry-derived observations of ice motion. Following a validation of ISSM with standard benchmarks, we present a demonstration of its capability in the case of the Greenland Ice Sheet. We show ISSM is able to simulate the ice flow of an entire ice sheet realistically at a high spatial resolution, with higher-order physics, thereby providing a pathway for improving projections of ice sheet evolution in a warming climate.Citation: Larour, E., H. Seroussi, M. Morlighem, and E. Rignot (2012), Continental scale, high order, high spatial resolution, ice sheet modeling using the Ice Sheet System Model (ISSM),

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Section: Discussionmentioning

confidence: 99%

Dynamically and Observationally Constrained Estimates of Water-Mass Distributions and Ages in the Global Ocean

DeVries

Primeau

2011

Journal of Physical Oceanography

180

202

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“…For GCMs with active ice shelves, a calving law is needed to release the tabular iceberg into the ocean. The question of what calving law to use is a topic of ongoing research [Benn et al, 2007;Alley et al, 2008;Levermann et al, 2012;Bassis and Jacobs, 2013] and is still unresolved. One potential way to temporarily bypass this problem would be to run hindcast simulations using historically observed calving events.…”

Section: Journal Of Advances In Modeling Earth Systems 101002/2017msmentioning

confidence: 99%

“…Since the focus of this study is on developing a framework for modeling tabular icebergs, we bypass the question of how to prescribe a physical calving law [Benn et al, 2007;Alley et al, 2008;Levermann et al, 2012;Bassis and Jacobs, 2013] by manually breaking off a semicircular iceberg. This is achieved by allowing all ice elements initially within a 14.4 km radius of the center of the ice front to move freely while the other ice elements continue to be held stationary.…”

Section: Iceberg Calvingmentioning

confidence: 99%

Modeling tabular icebergs submerged in the ocean

Stern

Adcroft

Sergienko

et al. 2017

J Adv Model Earth Syst

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Large tabular icebergs calved from Antarctic ice shelves have long lifetimes (due to their large size), during which they drift across large distances, altering ambient ocean circulation, bottom‐water formation, sea‐ice formation, and biological primary productivity in the icebergs' vicinity. However, despite their importance, the current generation of ocean circulation models usually do not represent large tabular icebergs. In this study, we develop a novel framework to model large tabular icebergs submerged in the ocean. In this framework, tabular icebergs are represented by pressure‐exerting Lagrangian elements that drift in the ocean. The elements are held together and interact with each other via bonds. A breaking of these bonds allows the model to emulate calving events (i.e., detachment of a tabular iceberg from an ice shelf) and tabular icebergs breaking up into smaller pieces. Idealized simulations of a calving tabular iceberg, its drift, and its breakup demonstrate capabilities of the developed framework.

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“…Although the shelf as a whole is in near hydrostatic balance with the ocean waters, the flow structure inside the ice shelf determines that it is a dynamic scenario of advancing-thinning-breaking, from groundling line toward the calving front. ''Along-flow spreading'' is believed the dominant control on ice shelf calving (Thomas 1973;Alley et al 2008;Winkelmann et al 2011). Ice shelves spread under their own weight and the imbalance pushes at the calving front and around the grounding line.…”

Section: The Calving Schemementioning

confidence: 99%

“…It is clear that the exact calving timing and sizes of the icebergs are not well simulated at present. To improve timing simulations of calving events, it may be necessary to include triggers such as pressure perturbations caused by long waves (compared with b k , otherwise cancellations are significant between positive and negative phases and net pressure in the vertical direction is small), tides, tsunamis, and collisions with passing icebergs, as suggested by Alley et al (2008) and more recently partially proved valid by Bromirski et al (2010). Further improvements of the results, higher resolution ice and bedrock geometry data (on sub-kilometer scale) are needed for the entire AIS, not only the peripheral areas, as initial seed cracks are difficult to capture for eastern Antarctica.…”

Section: Model Calvingmentioning

confidence: 99%

Verification of model simulated mass balance, flow fields and tabular calving events of the Antarctic ice sheet against remotely sensed observations

2012

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The Antarctic ice sheet (AIS) has the greatest potential for global sea level rise. This study simulates AIS ice creeping, sliding, tabular calving, and estimates the total mass balances, using a recently developed, advanced ice dynamics model, known as SEGMENT-Ice. SEGMENTIce is written in a spherical Earth coordinate system. Because the AIS contains the South Pole, a projection transfer is performed to displace the pole outside of the simulation domain. The AIS also has complex ice-watergranular material-bedrock configurations, requiring sophisticated lateral and basal boundary conditions. Because of the prevalence of ice shelves, a 'girder yield' type calving scheme is activated. The simulations of present surface ice flow velocities compare favorably with InSAR measurements, for various ice-water-bedrock configurations. The estimated ice mass loss rate during [2003][2004][2005][2006][2007][2008][2009] agrees with GRACE measurements and provides more spatial details not represented by the latter. The model estimated calving frequencies of the peripheral ice shelves from 1996 (roughly when the 5-km digital elevation and thickness data for the shelves were collected) to 2009 compare well with archived scatterometer images. SEG-MENT-Ice's unique, non-local systematic calving scheme is found to be relevant for tabular calving. However, the exact timing of calving and of iceberg sizes cannot be simulated accurately at present. A projection of the future mass change of the AIS is made, with SEGMENT-Ice forced by atmospheric conditions from three different coupled general circulation models. The entire AIS is estimated to be losing mass steadily at a rate of *120 km 3 /a at present and this rate possibly may double by year 2100.

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A Simple Law for Ice-Shelf Calving

Cited by 95 publications

References 1 publication

Dynamically and Observationally Constrained Estimates of Water-Mass Distributions and Ages in the Global Ocean

Dynamically and Observationally Constrained Estimates of Water-Mass Distributions and Ages in the Global Ocean

Modeling tabular icebergs submerged in the ocean

Verification of model simulated mass balance, flow fields and tabular calving events of the Antarctic ice sheet against remotely sensed observations

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