Quasi-decadal circumpolar variability of antarctic sea ice

Decadal variability of Antarctic sea ice and a role of ocean dynamics are examined with sea ice concentration (SIC) and sea surface temperature (SST) derived from satellite microwave observation and obtained by a high resolution coupled oceanatmosphere-ice general circulation model (CGCM). Sea ice observations revealed a circumpolar variability of sea ice edge (SIE) on quasi-decadal time scale. SST also showed variation on similar time scale with warm (cool) anomaly roughly corresponding to retreat (extension) of SIE at negative (positive) southern annular mode (SAM). CGCM run without anthropogenic forcing and volcanic eruptions revealed that the leading mode of SIC is quasicircumpolar pattern with a dominant time scale of 12-17 years and the leading mode of SST also has a similar pattern with the SIC showing a high degree of inverse correlation. The modeled SAM significantly correlates with these leading modes of both SIC and SST, representing the same structure with the observations. This indicates that the oceanic natural variability is the key to understand the quasi-decadal variability in sea ice.