Examining the impact of multiple climate forcings on simulated Southern Hemisphere climate variability

Abstract

The study examines the influence of external climate forcings, and atmosphere–ocean–sea–ice coupled interaction on the Southern Hemisphere (SH) atmospheric circulation variability. We analysed observed and simulated changes in view of Antarctic sea–ice and Southern Ocean surface temperature trends over recent decades. The experiment embraces both idealised and comprehensive methods that involves an Earth System Model (ESM) prototype. The sensitivity experiment is conducted in a manner that decomposes the signatures of sea–ice, sea surface temperature and feedback mechanisms. The results reveal that the Southern Annular Mode (SAM) multidecadal variability is found to be modulated by coupled interactions whereas its sub-seasonal to interannual vacillation seems to follow a random trajectory. The latter may strengthen the notion that its predictability is limited even with the use of ESMs. Most of the atmospheric circulation variability and recent changes may be explained by the ocean thermal forcing and coupled interactions. However, the influence of sea–ice forcing alone is largely indistinguishable and predominantly localised in nature. The result also confirms that the Antarctic dipole-like sea–ice pattern, a leading climate mode in the SH, has intensified in the last three decades irrespective of season. The probable indication is that processes within the Southern Ocean may play a key role, which deserves further investigation.