Antarctic ice sheet ensemble studies to better quantify uncertainties in sea level rise

Antarctic ice shelves are vulnerable to warming ocean temperatures and have already begun thinning in response to the changing climate. However, the Antarctic contribution to future sea level is still highly uncertain. Much of this uncertainty is due to inadequate model resolution and difficulty in process representation. We will present results from a 500-member ensemble of high resolution (4km) ice sheet simulations of Antarctica that are driven to the year 2200 by idealized (data-driven) ocean melt rate trajectories. We use the Community Ice Sheet Model (CISM) which is spun up for 20,000 years and reaches an ice-sheet configuration similar to present day. The ensemble probes a wide range of ocean melt rates including the extreme cases that reside in the tails of the probability distribution. Using this ensemble, we construct, validate and test an emulator of the Antarctic ice sheet. We will also show preliminary results of a new CISM ensemble informed by CMIP model output, in which the thermocline depth of the far-field ocean is varied in order to allow greater intrusion of warm deep water into the sub-shelf cavities.