Antarctic Sea Ice Response
Antarctic Sea Ice Response in Ensemble CMIP5 Historical and Ozone Perturbation Simulations
Antarctic sea-ice trends from three CMIP5 modelling systems are compared with observations. Several hypotheses advanced to explain the recent small positive trend in overall extent are investigated. In the CSIRO Mk3.6 system, area-weighted trends match the observations in some of the ensemble members. Whilst the CSIRO results with ozone forcing are more realistic, with regional patterns being enhanced in the Bellingshausen and Weddell seas and East Antarctica, we do not exclude the hypothesis that the current positive trend is due to natural variability. The regional patterns of ice advance and mid-winter ice maximum are well represented in the ACCESS modelling system and are driven by atmospheric pressure, air and ocean temperature trends; inclusion of ozone forcing did not have a discernible signal. The results do not support a hypothesis for regions of positive ice concentration trends being driven by increased stratification from sea-ice melting.