A new model to construct ice stream surface elevation profiles and calculate contributions to sea level rise

We present a method to numerically construct ice surface elevation profiles along a flowline centered on streaming ice flow, using a dynamical ice stream model. By applying conceivable climate warming-induced perturbations, we construct a new ice surface profile, giving us a volume change at the ice stream drainage basin-scale, assuming constant bed elevations. A summation of the volume changes for each ice stream drainage basin yields an estimate of ice sheet contributions to future sea level rise. Our ice stream model is one-dimensional, uses finite difference grid cells of 50-m resolution, and computes ice thickness based on the mass conservation law assuming steady state. Using a combination of surface and basal topography data, modeled surface mass balance values, and ice stream width data from velocity maps, we tune a parameter which quantifies the slipperiness at the base of the ice. Current surface profiles constructed using the slipperiness profiles match the observed surface profiles apart from the few places where slipperiness needs to be calibrated to values beyond those allowed by the physics of our model. Our model can therefore be seen as a framework that accommodates the full-range of ice-flow behaviors that are witnessed in the large polar ice streams today. Three perturbations - grounding line retreat, surface mass balance increase, and widening of ice stream widths - are applied on 9 ice streams in Greenland and Antarctica: Northeast Greenland Ice Stream, Jakobshavn Isbrae, Pine Island Glacier, Whillans Ice Stream, Bindschadler Ice Stream, Recovery Ice Stream, Shirase Glacier, Mellor Glacier, and Lambert Glacier. Of the 7 Antarctic cases, the largest and smallest losses come from Recovery Ice Stream (638km^3 per km width of ice) and Mellor Glacier (16km^3 per km width of ice), respectively. In terms of largest loss as a percentage of original volume stored in its drainage basin, Pine Island Glacier is the largest losing more than 25% of its originally stored volume that is contributable to sea level rise.