Abstract
AbstractPresent-day mass loss from the West Antarctic ice sheet is centred on the Amundsen Sea Embayment (ASE), primarily through ice streams, including Pine Island, Thwaites and Smith glaciers. To understand the differences in response of these ice streams, we ran a perturbed parameter ensemble, using a vertically-integrated ice flow model with adaptive mesh refinement. We generated 71 sets of three physical parameters (basal traction coefficient, ice viscosity stiffening factor and sub-shelf melt rate), which we used to simulate the ASE for 50 years. We also explored the effects of different bed geometries and basal sliding laws. The mean rate of sea-level rise across the ensemble of simulations is comparable with current observed rates for the ASE. We found evidence that grounding line dynamics are sensitive to features in the bed geometry: simulations using BedMap2 geometry resulted in a higher rate of sea-level rise than simulations using a rougher geometry, created using mass conservation. Modelled grounding-line retreat of all the three ice streams was sensitive to viscosity and basal traction, while the melt rate was more important in Pine Island and Smith glaciers, which flow through more confined ice shelves than Thwaites, which has a relatively unconfined shelf.
Highlights
The Amundsen Sea Embayment (ASE) in West Antarctica is the dominant region of ice mass loss from the Antarctic ice sheet (Shepherd and Wingham, 2007)
In this paper we investigate the sensitivity of Pine Island and Thwaites, along with the group including Smith Glacier that drain in to the Crosson Ice Shelf, to changes in model parameters, in order to understand how and why the ice streams differ in their behaviour
We report the sea-level contributions produced by the ensembles and how the grounding line retreat varied depending on the ensemble parameters
Summary
The Amundsen Sea Embayment (ASE) in West Antarctica is the dominant region of ice mass loss from the Antarctic ice sheet (Shepherd and Wingham, 2007). Ice drains through a number of ice streams, including Pine Island, Thwaites and Smith glaciers (Fig. 1). These ice streams rest on bedrock that is below sea level and generally slopes downwards towards the interior of the ice sheet (which is referred to as retrograde; prograde refers to bedrock sloping upwards towards the interior) (Holt and others, 2006; Vaughan and others, 2006). This configuration could be especially susceptible to grounding line retreat, through marine ice-sheet instability (Weertman, 1974). Observations have shown that the Pine Island Glacier grounding line retreated at an average rate of 0.95 ± 0.09 km a−1 between 1992 and 2011 (Park and others, 2013)
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