Abstract
Abstract Inaccurate representations of iceberg calving from ice shelves are a large source of uncertainty in mass-loss projections from the Antarctic ice sheet. Here, we address this limitation by implementing and testing a continuum damage-mechanics model in a continental scale ice-sheet model. The damage-mechanics formulation, based on a linear stability analysis and subsequent long-wavelength approximation of crevasses that evolve in a viscous medium, links damage evolution to climate forcing and the large-scale stresses within an ice shelf. We incorporate this model into the BISICLES ice-sheet model and test it by applying it to idealized (1) ice tongues, for which we present analytical solutions and (2) buttressed ice-shelf geometries. Our simulations show that the model reproduces the large disparity in lengths of ice shelves with geometries and melt rates broadly similar to those of four Antarctic ice shelves: Erebus Glacier Tongue (length ~ 13 km), the unembayed portion of Drygalski Ice Tongue (~ 65 km), the Amery Ice Shelf (~ 350 km) and the Ross Ice Shelf (~ 500 km). These results demonstrate that our simple continuum model holds promise for constraining realistic ice-shelf extents in large-scale ice-sheet models in a computationally tractable manner.
Highlights
The largest source of uncertainty in projections of future sea-level rise is the response of the Antarctic ice sheet to a warming climate (e.g. Pachauri and others, 2014; Edwards and others, 2021)
Because much of the West Antarctic ice sheet is grounded below sea level and ice flux across the grounding line depends strongly on the ice thickness there, the loss of buttressing affects the stability of the grounding line itself (Schoof, 2007; Joughin and Alley, 2011; Gudmundsson, 2013; Pegler, 2018; Martin and others, 2019)
Our continuum damage mechanics model, which simulates the evolution of the ratio of crevasse depth to ice thickness according to a pseudo-plastic necking instability, provides a useful framework for modeling damage evolution and terminus characteristics without introducing additional parameters
Summary
The largest source of uncertainty in projections of future sea-level rise is the response of the Antarctic ice sheet to a warming climate (e.g. Pachauri and others, 2014; Edwards and others, 2021). Horizontal stress gradients in these fringing shelves, associated with pinning points and embayment walls, reduce the ice flux across the grounding line by buttressing the upstream glaciers (e.g. Dupont and Alley, 2005; Goldberg and others, 2009; Gudmundsson, 2013; Pegler, 2018). The thermodynamics associated with large-scale ice-shelf melt are relatively well understood (Jenkins and Holland, 2007). Both the small- and large-scale physical rifting and fracturing processes controlling iceberg calving have proven more difficult to understand and model (Benn and others, 2007b). Calving changes the geometry of ice shelves through the production of icebergs, which can separate the ice from pinning points or embayment walls These detachments reduce the buttressing of ice shelves, increasing the ice flux across their grounding lines. Because much of the West Antarctic ice sheet is grounded below sea level and ice flux across the grounding line depends strongly on the ice thickness there, the loss of buttressing affects the stability of the grounding line itself (Schoof, 2007; Joughin and Alley, 2011; Gudmundsson, 2013; Pegler, 2018; Martin and others, 2019)
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