Persistent Antarctic sea ice biases in spite of recent observed sharp decline

Antarctic sea ice expanded for the first 35 years of the satellite record, but in the past 10 years has dropped to record lows. The recent unexpected behaviour has renewed discussion on the ability of coupled climate models to capture observations. Here, we present analysis of CMIP6 model output and satellite observations to argue the following. The clear observed Antarctic sea ice expansion from 1979 to around 2014 should be captured in state-of-the-art coupled climate model ensembles. However, only a very small fraction of models capture this expansion, and those that do almost universally show large biases in mean state and/or variability. Besides this, simulations that capture the post-2014 decline are also uncommon. These issues severely limit our ability to understand observed and future Antarctic sea ice change.