Twenty first century changes in Antarctic and Southern Ocean surface climate in CMIP6

A comprehensive understanding of how Antarctic climate may change across a range of scenarios is important for providing information on implications of different emissions pathways. Output from model simulations coordinated as part of the Coupled Model Intercomparison Project Phase 6 (CMIP6) provides an opportunity for a comprehensive analysis of the latest generation of state-of-the-art climate models, which follow a wider range of experiment types and scenarios than previous CMIP phases. Here the main broad-scale 21st century Antarctic projections provided by the CMIP6 models are shown across four forcing scenarios: SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5. End-of-century Antarctic surface-air temperature change across these scenarios (relative to 1995-2014) is 1.3, 2.5, 3.7 and 4.8 °C. The corresponding proportional precipitation rate changes are 8, 16, 24 and 31 %. In addition to these end-of-century changes, results will be shown from an assessment of scenario dependence of absolute and global-relative 21st century projections. Differences in regional response are of particular relevance to coastal Antarctica, where, for example, ecosystems and ice shelves are highly sensitive to the timing of crossing of key thresholds in both atmospheric and oceanic conditions. Overall it is found that projected zonal mean changes at latitudes of coastal Antarctica do not scale linearly with global forcing. We identify two factors that appear to contribute: (i) projected recovery of Southern Hemisphere stratospheric ozone and its effect on the mid-latitude westerlies associated changes in other climate variables and (ii) a continued Southern Ocean warming in low emissions stabilisation scenarios. Wider implications of these results will be discussed.