An observational study on the interactions between storm tracks and sea ice in the Southern Hemisphere

Using the lagged maximum covariance analysis (MCA), the present study investigates the interannual variability of the storm track in the Southern Hemisphere and the Antarctic sea ice throughout the year. The results show that the two are most tightly coupled in the austral cold seasons. Specifically, storm track anomalies in June and July are associated with a zonal dipole structure of the sea ice concentration (SIC) anomalies in the western Hemisphere, with centers in the Antarctic Peninsula and the Amundsen-Bellingshausen Seas. The storm track can modulate the large-scale atmospheric circulations, which induces anomalous meridional heat transport, downward longwave radiation, and mechanical forcing to further influence the SIC anomalies. The resultant SIC anomalies can last for several months and have the potential to feed back to the storm track. According to the MCA, the influence of the SIC anomalies to the storm track is most evident in August. The SIC dipole along with the SIC anomalies in the Indian Ocean sector have large impact on the storm track activities downstream. The SIC anomalies alters the near-surface temperature gradient and subsequently atmospheric baroclinicity. Further energetic analysis suggests that the enhanced atmospheric baroclinicity facilitates the baroclinic energy conversion from mean available potential energy to eddy available potential energy, and then to eddy kinetic energy, strengthening the storm track activities over the midlatitude Indian Ocean.