Biases in tropical Pacific teleconnections and ocean memory together limit spring sea ice predictability in dynamical models in the Weddell Sea

Antarctic sea ice plays a critical role in modulating global climate variability and in supporting polar ecosystems. However, sea ice seasonal forecasts continue to show limited skill in capturing interannual variability across key regions and seasons. Here we evaluate seasonal predictions of Antarctic sea ice extent predictions from six Copernicus Climate Change Service forecast systems, focusing on the Weddell Sea, where springtime skill deteriorates rapidly with lead time. We identify two systematic sources of model error. First, models show excessive persistence of winter sea ice anomalies compared to observations, indicating an overdependence on ocean conditions. Second, they fail to adequately represent large-scale atmospheric circulation anomalies associated with El Niño–Southern Oscillation and Southern Annular Mode interactions, underestimating Amundsen Sea Low pressure anomalies and related wind patterns. These circulation-related biases appear to originate from misrepresented atmospheric responses to tropical Pacific sea surface temperatures. Our results prompt us to revisit sea-ice ocean couplings and better capture tropical-Antarctic teleconnections in dynamic models to improve Antarctic sea ice prediction.