Seasonal Relationships between Large-Scale Climate Variability and Antarctic Sea Ice Concentration

• Published in: Journal of climate Vol. 25; no. 16; pp. 5451 - 5469
• Main Authors: Simpkins, Graham R., Ciasto, Laura M., Thompson, David. W. J., England, Matthew H.
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 15-08-2012
• Subjects: Anomalies; Antarctic Oscillation; Antarctic sea ice; Asymmetry; Atmospheric circulation; Atmospheric circulation anomalies; Atmospherics; Climate; Climate change; Climate variability; Cold season; Dipoles; Earth, ocean, space; El Nino; El Nino phenomena; El Nino-Southern Oscillation event; Exact sciences and technology; External geophysics; Global warming; Ice; Linkages; Marine; Meteorology; Oceans; Principal components analysis; Sea ice; Sea ice anomalies; Sea ice concentrations; Seas; Seasonal variability; Seasonal variations; Seasonality; Seasons; Southern Hemisphere; Southern Oscillation; Studies; Time series; Trends; Variability; Antarctic Ocean; Amundsen Sea; polar regions; Ross Sea; Antarctica; Antarctic Peninsula; PS, Ross Sea; Southern Hemisphere; trend-surface analysis; Southern Hemisphere annular mode; Summer; climate variability; anomalies; principal components analysis; El Nino; Southern oscillation; sea ice; Polar region; atmospheric circulation; seasonal variations; Composite analysis
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/jcli-d-11-00367.1

The observed relationships between anomalous Antarctic sea ice concentration (SIC) and the leading patterns of Southern Hemisphere (SH) large-scale climate variability are examined as a function of season over 1980–2008. Particular emphasis is placed on 1) the interactions between SIC, the southern annular mode (SAM), and El Niño–Southern Oscillation (ENSO); and 2) the contribution of these two leading modes to the 29-yr trends in sea ice. Regression, composite, and principal component analyses highlight a seasonality in SH sea ice–atmosphere interactions, whereby Antarctic sea ice variability exhibits the strongest linkages to the SAM and ENSO during the austral cold season months. As noted in previous work, a dipole in SIC anomalies emerges in relation to the SAM, characterized by centers of action located near the Bellingshausen/Weddell and Amundsen/eastern Ross Seas. The structure and magnitude of this SIC dipole is found to vary considerably as a function of season, consistent with the seasonality of the overlying atmospheric circulation anomalies. Relative to the SAM, the pattern of sea ice anomalies linked to ENSO exhibits a similar seasonality but tends to be weaker in amplitude and more diffuse in structure. The relationships between ENSO and sea ice also exhibit a substantial nonlinear component, highlighting the need to consider both season and phase of the ENSO cycle when diagnosing ENSO–SIC linkages. Trends in SIC over 1980–2008 are not significantly related to trends in either the SAM or ENSO during any season, including austral summer when the trend in the SAM is most pronounced.