Divergent trajectories of Antarctic ice shelf surface melt under 21st century climate scenarios

Monday, 15 December 2014: 12:05 PM
Luke D Trusel1,2, Karen E Frey1, Sarah B Das2, Peter Kuipers Munneke3 and Erik van Meijgaard4, (1)Clark University, Graduate School of Geography, Worcester, MA, United States, (2)Woods Hole Oceanographic Institution, Geology and Geophysics, Woods Hole, MA, United States, (3)Utrecht University, Institute for Marine and Atmospheric Research, Utrecht, Netherlands, (4)Royal Netherlands Meteorological Institute, De Bilt, Netherlands
Antarctic ice shelves represent a critical interface between continental ice masses and the surrounding ocean. Breakup events of several ice shelves in recent decades have been linked to an increase in intense surface melting, and have in turn lead to cascading effects including accelerated glacier discharge into the ocean. In this study, we utilized sophisticated regional and global climate models (GCMs) to assess potential future surface melt trajectories across Antarctica under two climate scenarios (RCP4.5 and RCP8.5). RACMO2.1, a polar-adapted regional atmospheric climate model, was forced by the ERA-Interim reanalysis (1980-2010) and by two GCMs, EC-EARTH and HadGEM2-ES (2007-2100). Using RACMO2.1, we observed an exponential growth function well represents the relationship between ice shelf surface meltwater production and mean summer (DJF) 2-meter air temperature (t2m). We employed this melt-t2m relationship to project melt using t2m output from an ensemble of five CMIP5-based GCMs incorporating the NCAR Community Land Model 4 (CLM4), following spatial downscaling and bias correction using t2m from ERA-Interim-forced RACMO2.1. Our resulting GCM-derived melt projections provide an independent and methodologically unique perspective into potential future melt pathways, complementary to those derived from RACMO2.1. Most notably, both RACMO2.1 and the CMIP5 ensemble reveal divergent trajectories of meltwater production beyond 2050 under the two climate scenarios. For many ice shelves in RCP4.5, meltwater production through 2100 remains at levels comparable to present. Conversely, under RCP8.5 all methods indicate non-linear melt intensification, resulting in a four-fold increase in the Antarctic-wide meltwater volume by the end of the 21st century. For some ice shelves, including Larsen C and Wilkins (Antarctic Peninsula), and Shackleton and West (Wilkes Land), spatially averaged end-of-century meltwater production within RCP8.5 approaches or surpasses levels historically associated with collapse of Antarctic Peninsula ice shelves (~600 mm w.e. a-1). While many factors influence ice shelf stability, these projections indicate a strong sensitivity of ice shelf melting to future climate pathways with potentially profound effects on future ice shelf stability.