Abstract
Abstract. We use the BISICLES adaptive mesh ice sheet model to carry out one, two, and three century simulations of the fast-flowing ice streams of the West Antarctic Ice Sheet, deploying sub-kilometer resolution around the grounding line since coarser resolution results in substantial underestimation of the response. Each of the simulations begins with a geometry and velocity close to present-day observations, and evolves according to variation in meteoric ice accumulation rates and oceanic ice shelf melt rates. Future changes in accumulation and melt rates range from no change, through anomalies computed by atmosphere and ocean models driven by the E1 and A1B emissions scenarios, to spatially uniform melt rate anomalies that remove most of the ice shelves over a few centuries. We find that variation in the resulting ice dynamics is dominated by the choice of initial conditions and ice shelf melt rate and mesh resolution, although ice accumulation affects the net change in volume above flotation to a similar degree. Given sufficient melt rates, we compute grounding line retreat over hundreds of kilometers in every major ice stream, but the ocean models do not predict such melt rates outside of the Amundsen Sea Embayment until after 2100. Within the Amundsen Sea Embayment the largest single source of variability is the onset of sustained retreat in Thwaites Glacier, which can triple the rate of eustatic sea level rise.
Highlights
The present-day West Antarctic Ice Sheet (WAIS) is experiencing an imbalance between the mass it receives as snowfall and that which it loses through discharge to the oceans (Rignot, 2008; Pritchard et al, 2009; Shepherd et al, 2012; Mouginot et al, 2014; Rignot et al, 2014)
We find that variation in the resulting ice dynamics is dominated by the choice of initial conditions and ice shelf melt rate and mesh resolution, ice accumulation affects the net change in volume above flotation to a similar degree
Within the Amundsen Sea Embayment the largest single source of variability is the onset of sustained retreat in Thwaites Glacier, which can triple the rate of eustatic sea level rise
Summary
The present-day West Antarctic Ice Sheet (WAIS) is experiencing an imbalance between the mass it receives as snowfall and that which it loses through discharge to the oceans (Rignot, 2008; Pritchard et al, 2009; Shepherd et al, 2012; Mouginot et al, 2014; Rignot et al, 2014). In several areas this has led to the persistent loss of ice amounting to a significant contribution to sea-level rise. The second is the technical difficulty involved in calculating the flow of ice across the ice sheet’s grounding line and the consequent grounding line
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