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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]

We investigate the spatio-temporal characteristics of the austral spring Ross Ice Shelf Polynya (RISP) and its relationship with atmospheric circulation anomalies based on the sea ice concentration data from the National Snow and Ice Data Center (NSIDC) and the ERA5 reanalysis data. The RISP area series is derived by choosing 25% sea ice concentration as the threshold. Then the principal spatial patterns of the RISP are acquired by using the empirical orthogonal function (EOF) analysis. The leading EOF (EOF1) has a spatial distribution of a strong negative core in the northeastern RISP with a weak positive core near the Cape Adare, explaining 48.1% of the variance. This mode matches the wind pattern of the northwesterly on the western Ross Sea while southwesterly on the eastern Ross Sea, which reflects the zonal variation of the RISP. There is also a strong positive correlation between the RISP area and the PC1. The EOF2 explains 27.4% of the variance, and is mainly characterized by a large region of low values in the northwestern Ross Sea with a small region of high value near Cape Colbeck. Matching the strong southerly over the western Ross Sea, the EOF2 partly depicts the meridional variation of the RISP. We further explored the connections between the RISP and sea level pressure, and found that a deeper and more eastward Amundsen Sea Low (ASL) in November often coincides with a larger and more eastward RISP in December. This lagged response is partly generated through the influence of the ASL on the RISP in November. [ABSTRACT FROM AUTHOR]

Satellite-derived Antarctic sea ice extent has displayed a slight upward since 1979, but with strong temporal and regional variability—the drivers of which are poorly understood. Here, we conduct numerical experiments with a circum-Antarctic ocean–sea ice–ice shelf model driven by realistic atmospheric surface boundary conditions to examine the factors responsible for the temporal and spatial patterns in observed Antarctic sea ice variability. The model successfully reproduces observed seasonal and interannual variability in total sea ice extent and the temporal/spatial patterns of sea ice concentration and seasonality (days of advance and retreat and actual ice days) for 1979–2014. Sensitivity experiments are performed, in which the interannual variability in wind stress or thermodynamic surface forcing is ignored, to delineate their contributions to Antarctic sea ice fields. The results demonstrate that: (1) thermodynamic forcing plays a key role in driving interannual variability in sea ice extent and seasonality in most Antarctic sectors; (2) only in the Ross Sea the wind stress does become the main driver of sea ice extent variability; (3) thermodynamic forcing largely regulates interannual variability in the timing of sea ice advance, while wind stress largely controls the timing of the sea ice retreat; and (4) although both wind stress and thermodynamic forcing contribute to variability in total sea ice volume, the wind stress plays a dominant role in regulating sea ice volume variability in the near-coastal zone. [ABSTRACT FROM AUTHOR]