The stability of grounding lines on retrograde slopes

Gudmundsson, G. Hilmar; Krug, Jean; Durand, G.; Favier, Lionel; Gagliardini, Olivier

doi:10.5194/tc-6-1497-2012

Cited by 259 publications

(360 citation statements)

References 28 publications

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“…In contrast to the flow-line configuration the threedimensional setup inherently accounts for the buttressing effect in the initial steady-state simulation due to the presence of a confined ice shelf (Dupont and Alley, 2005;Gudmundsson et al, 2012). However, the ice shelf is removed in the course of perturbation to prevent scale-dependent influences that would originate from a forcing through sub-shelf melting, surface accumulation or ice softness.…”

Section: Resultsmentioning

confidence: 99%

“…For the scaling experiments the bed geometry (b x and b y ) and the parameters a, A and C are multiplied with the scaling ratios from to Table 2. The terms "BC-300" and "BC0" refer to the bed geometries described in Feldmann and Levermann (2015a) and b y,G refers to y component of the bed topography used in Gudmundsson et al (2012). Table 2.…”

Section: Two-dimensional Case With Time and Length Scales For Both Homentioning

confidence: 99%

“…For the three-dimensional experiments we extend our flowline geometry by introducing a second horizontal dimension (y) to obtain channel-like ice flow in three dimensions with similar geometry to that in Gudmundsson et al (2012) and Asay-Davis et al (2015). The bed topography b(x, y) is a superposition of two components: the bed component in x direction, b x (x), is as described in Feldmann and Levermann (2015a) but lowered uniformly by −300 m (Fig.…”

Section: C2 Three-dimensional Simulationsmentioning

confidence: 99%

“…In particular we assume isothermal ice and a spatially uniform basal friction coefficient, conditions that have been used to analyze ice-sheet dynamics in a number of previous studies (e.g., Dupont and Alley, 2005;Goldberg et al, 2009;Gudmundsson et al, 2012;Pattyn et al, 2013;AsayDavis et al, 2015). Neglecting the terms of vertical shearing in the stress balance and accounting for the small thicknessto-length ratio of ice sheets, the SSA represents the relevant dynamics of floating ice shelves and grounded ice streams.…”

Section: Introductionmentioning

confidence: 99%

“…Neglecting the terms of vertical shearing in the stress balance and accounting for the small thicknessto-length ratio of ice sheets, the SSA represents the relevant dynamics of floating ice shelves and grounded ice streams. The capability of numerical SSA models to simulate these regimes that are characterized by fast plug-like flow has been demonstrated in various studies (e.g., Goldberg et al, 2009;Gudmundsson et al, 2012). The SSA can be complemented by the SIA (Huybrechts, 1990;Sato and Greve, 2012) to also include vertical shearing, which is dominant in the more stagnant interior parts of an ice sheet (Bueler and Brown, 2009;Pollard and DeConto, 2012;Thoma et al, 2015), whereas higher-order approximations (Schoof and Hindmarsh, 2010;Larour et al, 2012;Cornford et al, 2015) neglect less stress components in the full Stokes stress balance .…”

Section: Introductionmentioning

confidence: 99%

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Similitude of ice dynamics against scaling of geometry and physical parameters

Feldmann

Levermann

2016

The Cryosphere

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Abstract. The concept of similitude is commonly employed in the fields of fluid dynamics and engineering but rarely used in cryospheric research. Here we apply this method to the problem of ice flow to examine the dynamic similitude of isothermal ice sheets in shallow-shelf approximation against the scaling of their geometry and physical parameters. Carrying out a dimensional analysis of the stress balance we obtain dimensionless numbers that characterize the flow. Requiring that these numbers remain the same under scaling we obtain conditions that relate the geometric scaling factors, the parameters for the ice softness, surface mass balance and basal friction as well as the ice-sheet intrinsic response time to each other. We demonstrate that these scaling laws are the same for both the (two-dimensional) flow-line case and the three-dimensional case. The theoretically predicted ice-sheet scaling behavior agrees with results from numerical simulations that we conduct in flow-line and three-dimensional conceptual setups. We further investigate analytically the implications of geometric scaling of ice sheets for their response time. With this study we provide a framework which, under several assumptions, allows for a fundamental comparison of the ice-dynamic behavior across different scales. It proves to be useful in the design of conceptual numerical model setups and could also be helpful for designing laboratory glacier experiments. The concept might also be applied to real-world systems, e.g., to examine the response times of glaciers, ice streams or ice sheets to climatic perturbations.

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Section: Resultsmentioning

confidence: 99%

Section: Two-dimensional Case With Time and Length Scales For Both Homentioning

confidence: 99%

Section: C2 Three-dimensional Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Similitude of ice dynamics against scaling of geometry and physical parameters

Feldmann

Levermann

2016

The Cryosphere

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Understanding controls on rapid ice‐stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model

et al. 2014

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[1] Using a one-dimensional numerical model of ice-stream flow with robust grounding-line dynamics, we explore controls on paleo-ice-stream retreat in Marguerite Bay, Antarctica, during the last deglaciation. Landforms on the continental shelf constrain the numerical model and suggest that retreat was rapid but punctuated by a series of slowdowns. We investigate the sensitivity of ice-stream retreat to changes in subglacial and lateral topography and to forcing processes including sea-level rise, enhanced melting beneath an ice shelf, atmospheric warming, and ice-shelf debuttressing. Our experiments consistently reproduce punctuated retreat on a bed that deepens inland, with retreat-rate slowdowns controlled by narrowings in the topography. Sensitivity experiments indicate that the magnitudes of change required for individual forcing mechanisms to initiate retreat are unrealistically high but that thresholds are reduced when processes act in combination. The ice stream is, however, most sensitive to ocean warming and associated ice-shelf melting, and retreat was most likely in response to external forcing that endured throughout the period of retreat rather than to a single triggering "event." Timescales of retreat are further controlled by the delivery of ice from upstream of the grounding line. Due to the influence of topography, modeled retreat patterns are insensitive to the temporal pattern of forcing evolution. We therefore suggest that despite regionally similar forcing mechanisms, landscape controls significant contrasts in retreat behavior between adjacent but topographically distinct catchments. Patterns of ice-stream retreat in the past, present, and future should therefore be expected to vary significantly.

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Antarctic outlet glacier mass change resolved at basin scale from satellite gravity gradiometry

Bouman¹,

Fuchs²,

Ivins

et al. 2014

Geophysical Research Letters

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The orbit and instrumental measurement of the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite mission offer the highest ever resolution capabilities for mapping Earth's gravity field from space. However, past analysis predicted that GOCE would not detect changes in ice sheet mass. Here we demonstrate that GOCE gravity gradiometry observations can be combined with Gravity Recovery and Climate Experiment (GRACE) gravity data to estimate mass changes in the Amundsen Sea Sector. This refined resolution allows land ice changes within the Pine Island Glacier (PIG), Thwaites Glacier, and Getz Ice Shelf drainage systems to be measured at respectively −67 ± 7, −63 ± 12, and −55 ± 9 Gt/yr over the GOCE observing period of November 2009 to June 2012. This is the most accurate pure satellite gravimetry measurement to date of current mass loss from PIG, known as the “weak underbelly” of West Antarctica because of its retrograde bed slope and high potential for raising future sea level.

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The stability of grounding lines on retrograde slopes

Cited by 259 publications

References 28 publications

Similitude of ice dynamics against scaling of geometry and physical parameters

Similitude of ice dynamics against scaling of geometry and physical parameters

Understanding controls on rapid ice‐stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model

Antarctic outlet glacier mass change resolved at basin scale from satellite gravity gradiometry

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