An Examination of ENSO signal in Antarctic Circumpolar Current Region Revealed By NCAR Climate System Model Simulations

What is the trigerring cause of El Nino? There have been many hypotheses, most of them suggest that the onset of an El Nino is a result of the nonlinear processes internal to the coupled atmosphere-ocean system in the tropical Pacific Ocean. This study examines a new hypothesis which is based on a recently found interesting phonomenon in the southern polar ocean - Antarctic Circumpolar Wave. This study looks into tropical-polar links to find possible triggering cause of El Nino onset.

It has been found that the warm sea surface temperature anomaly in the Antarctic Circumpolar Current (ACC) propagates eastward at a 4-5 year period circling Antarctica. It also stretches northeastward across most of the subtropical South Pacific. Part of it turns north branching off into Peru Current where happened to be El Nino birth place. Is this warm anomaly originated from the ACC a possible triggering cause of the onset of an El Nino event?

A recent study validated the ability of NCAR Climate System Model (CSM)in capturing El Nino time scale variations (Liang,1998). The results from fully coupled CSM experiments provide us better data to examine our hypothesis that links tropical Pacific El Nino to Antarctic Circumpolar Wave. We re-examine El Nino signals in southern oceans in the NCAR CSM 300-year fully coupled simulation and further explore evidences that links Antarctic Circumpolar Wave to El Nino onset from the NCAR CSM 1870-1998's historical simulation.