Air–sea coupling over the Tasman Sea intensifies the ENSO-related South Pacific atmospheric teleconnection

Abstract

The ENSO-induced Pacific–South America (PSA) pattern is an important atmospheric bridge in linking the Antarctic climate to the tropical Pacific. The AGCM simulated PSA-like responses to ENSO are evidently weaker than the observed in terms of its intensity due to the lack of air–sea coupling processes. The Tasman Sea features active air–sea interactions. However, how and to what extent the air–sea coupling explains the deficiency of the AGCM responses to ENSO is unclear. In this study, the role of the air–sea coupling elsewhere the tropical Pacific in shaping the ENSO–South Pacific teleconnection is first estimated by comparing the coupled tropical Pacific pacemaker experiments (PACE) derived from the Community Earth System Model version 1 (CESM1) and the parallel Pacific Ocean–Global Atmosphere experiments (POGA) with the same atmospheric component model of CESM1. Our results suggest that the air–sea coupling elsewhere the tropical Pacific greatly intensifies the South Pacific atmospheric response to ENSO. Then the separated impact of air–sea coupling over the Tasman Sea is stressed with another set of AGCM experiments forced with the PACE sea surface temperature (SST) outputs in the Tasman Sea. The results show that the atmospheric response to the SST anomalies in the Tasman Sea bears a remarkable resemblance to that due to the air–sea coupling elsewhere the tropical Pacific, and explains about 30% of the intensified amplitude. This highlights a substantial contribution of the air–sea coupling over the Tasman Sea to intensifying the extratropical South Pacific atmospheric responses to ENSO, and provides a new perspective on the connection between tropical Pacific and Antarctic climate change.

Keywords

• Tasman Sea
• Air–sea coupling
• ENSO–South Pacific atmospheric teleconnection