Intraseasonal Variability of Antarctic Sea-Ice in Austral Winter Related to ENSO and SAM Events

Intraseasonal variability of Antarctic sea-ice concentration is investigated during austral winter using a 5-60 day band-pass filter and Empirical Orthogonal Function (EOF) analysis over the period 1995 to 2014. Zonal wave number three dominated in the Antarctic, especially so across the west Antarctic. Results showed the coexistence of stationary and propagating wave components. A spectral analysis of the first two PCs showed a similar structure for periods up to 15 days but generally more power in PC1 at longer periods. Regression analysis upon atmospheric fields using the first two PCs of sea-ice concentration showed a coherent wave number three pattern. The spatial phase delay between the sea ice and mean sea level pressure patterns suggests that meridional flow and associated temperature advection are important for modulating the sea ice field. EOF analyses carried out separately for El Niño, La Niña and neutral years, and for Southern Annular Mode positive, negative, and neutral periods, suggest that the spatial patterns of wave number 3 shift between subsets, suggesting that El Niño-Southern Oscillation (ENSO) and Southern Annular Mode (SAM) affect stationary wave interactions between sea-ice and atmospheric fields on intraseasonal time scales.