Century-scale simulations of the response of the West Antarctic Ice Sheet to a warming climate

Abstract

International audienceWe 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

Uneven onset and pace of ice‐dynamical imbalance in the Amundsen Sea Embayment, West Antarctica

“…Under persistent future oceanic forcing, models indicate that thinning will expand to larger areas in the PIG and THG basins, which would contribute to accelerated ice-mass loss and associated sea-level rise [e.g., Joughin et al, 2010Joughin et al, , 2014Cornford et al, 2015]. However, the nonuniform pace of drawdown spreading gives rise to the possibility that the spreading may be decelerated [Joughin et al, 2010] or even cease in certain regions.…”

“…Modeling studies have indicated that rates of ice discharge from this sector are expected to further grow in future, in part due to ongoing ice dynamics and in part due to projected ocean warming [Joughin et al, 2010[Joughin et al, , 2014Favier et al, 2014;Seroussi et al, 2014;Cornford et al, 2015;Goldberg et al, 2015].…”

Self-affine subglacial roughness: consequences for radar scattering and basal water discrimination in northern Greenland

“…Price et al, 2011;Seroussi et al, 2013;Nowicki et al, 2013;Shannon et al, 2013;Sergienko et al, 2014;Ritz et al, 2015;Cornford et al, 2015). Notably, the basal traction parameterisation -which encapsulates the thermal state, basal roughness, and lithology -is potentially the largest single geophysical uncertainty in projections of the response of ice sheets to climate change (Ritz et al, 2015).…”

Sea-level response to melting of Antarctic ice shelves on multi-centennial timescales with the fast Elementary Thermomechanical Ice Sheet model (f.ETISh v1.0)

“…Since then several marine ice sheet models of the Antarctic ice sheet have been developed, with varying ways of treating the grounding line, i.e. by increasing locally spatial resolution at the grounding line (Favier et al, 2014;Cornford et al, 2015), by making use of local interpolation strategies at the grounding line (Feldmann et al, 2014;Feldmann and Levermann, 2015;Golledge et al, 2015;Winkelmann et al, 2015) or by parametrizing grounding-line flux based on boundary layer theory (Pollard and DeConto, 2009;Pollard et al, 2015;DeConto and Pollard, 2016).…”