Abstract
Abstract. Floating ice shelves exert a stabilizing force onto the inland ice sheet. However, this buttressing effect is diminished by the fracture process, which on large scales effectively softens the ice, accelerating its flow, increasing calving, and potentially leading to ice shelf breakup. We add a continuum damage model (CDM) to the BISICLES ice sheet model, which is intended to model the localized opening of crevasses under stress, the transport of those crevasses through the ice sheet, and the coupling between crevasse depth and the ice flow field and to carry out idealized numerical experiments examining the broad impact on large-scale ice sheet and shelf dynamics. In each case we see a complex pattern of damage evolve over time, with an eventual loss of buttressing approximately equivalent to halving the thickness of the ice shelf. We find that it is possible to achieve a similar ice flow pattern using a simple rule of thumb: introducing an enhancement factor ∼ 10 everywhere in the model domain. However, spatially varying damage (or equivalently, enhancement factor) fields set at the start of prognostic calculations to match velocity observations, as is widely done in ice sheet simulations, ought to evolve in time, or grounding line retreat can be slowed by an order of magnitude.
Highlights
The largest uncertainties in sea level rise prediction are the dynamic ice sheet contributions (Jevrejeva et al, 2016)
Mass loss from ice shelves does not contribute to sea level rise directly but rather via the restraint ice shelves apply to the ice discharge from inland to ocean across the grounding line; in other words, mass loss from ice shelves is expected to weaken their buttressing effect
The acceleration caused by this ice shelf weakening results in the grounded ice thinning and in turn the grounding line retreats, by around 70 km in the first 100 years of the simulation and a further 30 km over the full 1000-year simulation
Summary
The largest uncertainties in sea level rise prediction are the dynamic ice sheet contributions (Jevrejeva et al, 2016). Calving is directly responsible for a mass loss comparable to that from ice shelf basal melting (Rignot et al, 2010; Depoorter et al, 2013; Liu et al, 2014). Increased rates of calving and basal melt seem intertwined and act in concert to enhance mass loss from ice shelves that are in negative mass balance under the present climate (Liu et al, 2014; Åström et al, 2014). To better predict the future evolution of the ice sheets, processes related to calving should be better understood and described
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