Abstract
ABSTRACTWe performed an Empirical Orthogonal Function (EOF) analysis to assess the intraseasonal variability of 5–60 day band-pass filtered Antarctic sea-ice concentration in austral winter using a 20-year daily dataset from 1995 to 2014. Zonal wave number 3 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 principal components (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 3 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. The results also indicate that El Niño-Southern Oscillation and Southern Annular Mode affect stationary wave interactions between sea-ice and atmospheric fields on intraseasonal timescales.
Highlights
It is well-known that the southern ocean including the Antarctic (Fig. 1) is an active component in the global climate system, and there are various interactions between atmospheric, oceanic and sea-ice fields
Spatial wave number 3 dominates in the marginal sea-ice zone in both Empirical Orthogonal Function (EOF), and the amplitude is large across the west Antarctic especially, in comparison with the east Antarctic
We performed an EOF analysis to assess the intraseasonal variability of 5–60 day band-pass filtered sea-ice concentration in the Antarctic in austral winter using a 20-year daily dataset spanning from 1995 through 2014
Summary
It is well-known that the southern ocean including the Antarctic (Fig. 1) is an active component in the global climate system, and there are various interactions between atmospheric, oceanic and sea-ice fields. In the Pacific sector of the Antarctic, many papers point out the relationship between El Niño-Southern Oscillation (ENSO) and sea-ice cover (e.g., Yuan, 2004; Harangozo, 2006; Zhang, 2014). The PacificSouth American (PSA) teleconnection pattern is characterized by a stationary Rossby wave train from the tropical central Pacific to tip of South America via the Amundsen– Bellingshausen Seas and is often excited by ENSO variability (e.g., Mo, 2000). The PSA and blocking both have a strong influence on Antarctic sea ice extent across the south Pacific (e.g., Renwick, 2002). Such studies find stationary waves in the atmosphere to be related to sea-ice variability
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