Recent studies have identified widespread vulnerable ice shelf regions in Antarctica which are both highly buttressed and susceptible to crevasse hydrofracturing, raising concern for potential crevasse driven ice‐shelf collapse and future sea level rise. Here, we employ the finite element ice flow model, Úa, to investigate whether crevasses which have propagated through the entire ice column have a significant impact on upstream flow and quantify their contribution to sea level rise. We find a large variability in the response of ice shelves to this perturbation, with changes in grounding line flux as large as 155% for the Filchner‐Ronne and 46% for the Ross, when compared to the present day. Crevasses located close to the grounding lines contribute most of this change. When compared to a second perturbation in which ice shelves are completely removed, however, the response is relatively small for all modeled ice shelves.

<div> <p>Antarctic Ice shelves are fundamentally important components of the cryosphere and key to predictions of global sea level rise. Thinning and fracturing of ice shelf systems can reduce back-stress forces exerted on grounded glaciers upstream, increasing mass flux across their grounding lines (GL). In recent years it has been suggested that a number of ice shelves around Antarctica have rapidly broken apart as a result of hydrofracturing.  Hydrofracture is the process whereby surface crevasses are filled up with meltwater and the resulting hydrostatic pressure cause outward propagation of the crevasse fracture.</p> <p>Recent work assessed the impact of ice shelf thickness change and crevasse hydrofracturing on the vulnerability of ice shelves and on ice drainage. Using a deep convolutional neural network, high-resolution crevasses and fractures were mapped throughout Antarctica, revealing that 60 ± 10 % of ice shelves are vulnerable to fracturing, if inundated with water.</p> <p>Here we use these crevasse maps to evaluate their impact on the flow of upstream glaciers, quantifying the change in flux at the GL. We employ a finite element ice flow model, Ua, which solves the vertically integrated shallow shelf approximation with an unstructured mesh, that allows refined resolution in complex areas, such as at the GL. In the absence of information on crevasse depth, we make the assumption that crevasses propagate through the entire thickness, meaning our results represent the maximum possible effect that these crevasses may have on ice flow. We present results for many of the most important ice shelves in East and West Antarctica.</p> <p>We find that incorporating crevasses in the ice shelf always increases the mass flux of upstream glaciers across their GLs, however, there is substantial variability in flux change among ice shelves. Small increases in flux due to crevassing (7-15%) were detected for Fimbul, Shackleton, Pine Island, Larsen C, and Brunt Ice Shelves, with a more considerable increase for the Dotson & Crosson Ice shelves (38%). The increase in flux due to crevassing was extremely large for the Totten Ice Shelf (248%). The large differences in sensitivity between ice shelves may be a result of various factors, most notably the proximity of the features identified as crevasses to important pinning points. More work investigating these factors is needed in order to have a more complete understanding of the effects of crevasse hydrofracturing on inland glaciers.</p> </div>

<p>The lightly grounded portion of the Whillans Ice Stream (WIS, Siple Coast, Antarctica), has a unique stick-slip motion behaviour, where prolonged stagnant phases (6-25 hrs) are interrupted by rapid active slip events (up to 0.5 m in < 1 hr).  WIS is also interesting because it is currently stagnating, presenting an important opportunity to understand this behaviour and its effect on future sea level rise. Detailed observations and a variety of modelling approaches have revealed the complexity of stick-slip behaviour and the importance of correctly representing ice rheology, ice stream geometry, spatial variability of friction strength, and boundary conditions. Currently, no single model exists that can fully replicate all the observed features of stick-slip motion as observed on the Whillans Ice Plain. Here we describe a full-Stokes viscoelastic finite element model that has been previously used to explore tidal modulation of ice stream flow, and which can overcome some of the assumptions adopted in previous work. The model is  set up for an idealised configuration of the Whillans Ice Plain, with the aim of exploring how the inclusion of relevant additional physics affects stick-slip motion for a rate and state friction law, and whether other sliding laws could also explain the observed motion. Ultimately, this modelling work aims to put tighter constraints on the conditions required to initiate stick-slip behaviour, improving our understanding of basal sliding and future sea level rise.</p>