Grounding line movement and ice shelf buttressing in marine ice sheets

Abstract

[1] Understanding the dynamics of marine ice sheets is integral to studying the evolution of the Antarctic ice sheet in both the short and long terms. An important component of the dynamics, grounding line migration, has proved difficult to represent in numerical models, and most successful attempts have made use of techniques that are only readily applicable to flow line models. However, to capture the stress transmission involved in another important component, the buttressing of a marine ice sheet by its ice shelf, the transverse direction must also be resolved. We introduce a model that solves the time-dependent shelfy stream equations and makes use of mesh adaption techniques to overcome the difficulties typically associated with the numerics of grounding line migration. We compare the model output with a recent benchmark for flow line models and show that our model yields an accurate solution while using far less resources than would be required without mesh adaption. We also show that the mesh adapting techniques extend to two horizontal dimensions. Experiments are carried out to determine how both ice shelf buttressing and ice rises affect the marine instability predicted for an ice sheet on a foredeepened bed. We find that buttressing is not always sufficient to stabilize such a sheet but collapse of the grounded portion is still greatly delayed. We also find that the effect of an ice rise is similar to that of narrowing the ice shelf.

The sedimentary legacy of a palaeo-ice stream on the shelf of the southern Bellingshausen Sea: Clues to West Antarctic glacial history during the Late Quaternary

“…A recent theoretical, glaciological study concluded that ice shelves fringing marine-based ice streams have a major buttressing effect (Goldberg et al, 2009). Therefore, the ice shelf of the ice stream flowing through Belgica Trough may also have delayed post-LGM grounding-line retreat and contributed to the observed slow and prolonged retreat pattern (Fig.…”

On the reconstruction of palaeo-ice sheets: Recent advances and future challenges

“…Most importantly, the Schoof (2007) formula includes a parameter that represents buttressing from an ice shelf. Buttressing is crucial because it opposes the tendency of the ice to spread and thin at the grounding-line, and can inhibit retreat and augment advance (Goldberg et al, 2009). Again, numerical experiments indicate that the Schoof (2007) formula is accurate in the presence of specified buttressing (Drouet et al, 2013), but it is also true that representing buttressing by a parameter diverts attention from the interplay between flow across the grounding line and the buttressing from an ice shelf.…”

Similitude of ice dynamics against scaling of geometry and physical parameters

“…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.…”

“…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 .…”