Intraseasonal Variability of Antarctic Sea Ice: A Regional Approach

In recent years, intraseasonal tropical variability has been shown to impact the mid- and high-latitude atmosphere and subsequently project onto surface fields such as surface temperature, snow depth and sea ice concentration. Convection associated with the leading mode of intraseasonal variability of the tropical atmosphere, the Madden-Julian Oscillation (MJO), can excite Rossby wave trains linking the extratropics with the tropics. For sea ice concentration modulation in particular, the majority of recent studies to date have focused on potential tropical-to-Arctic linkages, whereas our understanding of connections between intraseasonal tropical variability and Antarctic sea ice lags that of the Northern Hemisphere. This study builds on previous work by examining the time-lagged response of Antarctic sea ice concentration to tropical MJO forcing, with specific focus on assessing daily sea ice variabilty regionally. Anomalous daily change of sea ice concentration from the NOAA 25km x 25km climate data record product from NSIDC over a 30-year period from 1989-2018 was filtered and binned by phase of MJO using the Wheeler and Hendon index, for 0 to 20-day lag intervals. Coherent areas of statistically significant anomalous daily change were assessed in five distinct regions: the Ross Sea, the Weddell Sea, the Indian Ocean, the Bellingshausen and Amundsen Seas, and the Western Pacific Sea, along with other surface fields such as sea level pressure and 10 m winds. Correlations between anomalous daily change in sea ice concentration (SIC) and both meridional wind and 2-m temperature are assessed to quantify the relation between the MJO and Antarctic SIC. Results indicate sea ice anomalies vary both regionally and at different lag intervals, with the Weddell Sea and Indian Ocean sectors being most sensitive to intraseasonal influence.