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An operational synoptic-scale sea ice forecasting system for the Southern Ocean, namely Southern Ocean Ice Prediction System (SOIPS), has been developed to support ship navigation in the Antarctic sea ice zone. Practical application of the SOIPS forecasts had been implemented for the 38th Chinese National Antarctic Research Expedition for the first time. The SOIPS is configured on an Antarctic regional sea-ice‒ocean‒ice-shelf coupled model and an ensemble-based Localized Error Subspace Transform Kalman Filter data assimilation model. Daily near-real-time satellite sea ice concentration observations are assimilated into the SOIPS to update sea ice concentration and thickness in the 12 ensemble members of model state. By evaluating the SOIPS performance on forecasting sea ice metrics in a complete melt-freeze cycle from October 1, 2021 to September 30, 2022, this study shows that the SOIPS can provide reliable Antarctic sea ice forecasts. In comparison with the OSISAF data, annual mean root mean square errors of the sea ice concentration forecasts at leading time of up to 168-hour are lower than 0.19, and the integrated ice-edge errors of sea ice forecasts in most freezing months at leading times of 24-hour and 72-hour maintain around 0.5 × 106 km2 and below 1.0 × 106 km2, respectively. With respect to the scarce ICESat-2 observations, the mean absolute errors of the sea ice thickness forecasts at leading time of 24-hour are lower than 0.3 m, which is in range of the ICESat-2 uncertainties. Specifically, the SOIPS has a promised capacity in forecasting sea ice drift, both in magnitude and direction. The derived sea ice convergence rate forecasts have a high potential in supporting ship navigation on local fine scale. [ABSTRACT FROM AUTHOR]

The sea ice cover has experienced substantial changes in Antarctica in the past decades, yet its responses to the long-term trend of the local atmosphere are still not clear. With the aid of an Antarctic coupled sea ice-ocean-ice shelf model, the sea ice seasonality in response to the long-term trend of the local atmospheric forcing has been quantified based on a sea ice budget analysis. Significantly spatial variabilities have been found in the Antarctic sea ice in response to the long-term trend of the local atmospheric forcing. The sea ice area and volume decrease in the Weddell Sea and increase in the Ross Sea throughout the year. In the Amundsen-Bellingshausen Seas sector, the sea ice area decreases from December to June and increases from July to November, while the sea ice volume decreases throughout the year. In the Indian-Western Pacific Oceans sector, the sea ice area decreases from January to May and increases from June to December, while the sea ice volume increases throughout the year. The long-term trend of the local atmospheric forcing modulates the sea ice loss in the melting period mainly through modifying the ice-ocean heat flux over the ice base, while it governs the sea ice growth in the freezing period by the combined effects of the ice-ocean heat flux and the atmosphere-ocean heat flux. Although the trend of the surface wind can also lead to distinct variations by the local sea ice convergence/divergence, the integrated contributions over the basin scale are relatively small. [ABSTRACT FROM AUTHOR]