16.5
The influence of the Antarctic circumpolar wave on El Niņo from 1950 to 2001
Warren B. White, SIO/Univ. Of California, La Jolla, CA; and J. L. Annis
We find the slow eastward propagation of covarying surface temperature (ST) and sea level pressure (SLP) anomalies in the Antarctic Circumpolar Wave (ACW) persisting from 1950 to 2001, its path extending to within 25° latitude of equator in the Indian and South Pacific oceans, allowing it to influence El Niņo in the eastern equatorial Pacific Ocean along two different paths. Before 1977, El Niņo was initiated by the slow eastward propagation of covarying warm ST and low SLP anomalies across the subtropical South Pacific Ocean to South America, then equatorward along the eastern boundary to the equator. During this epoch, we find the ACW in the South Pacific Ocean displaced equatorward into the subtropics, where its warm phase accounted for the eastward propagation of warm ST and low SLP anomalies that initiated El Niņo before 1977. After 1977, El Niņo was initiated by the slow eastward propagation of covarying warm ST and low SLP anomalies across the equatorial Pacific Ocean. During this epoch, we find the ACW in the South Pacific Ocean displaced poleward into the high-latitudes, able to exert only weak and intermittent influence on El Niņo from that quarter. However, the ACW in the Indian Ocean was displaced equatorward into the subtropics during this epoch, where it spawned a north branch directed equatorward into the Warm Pool north of Australia, its warm phase accounting for the eastward propagation of warm ST and low SLP anomalies that initiated El Niņo after 1977.
Session 16, Interdecadal and Longer Term Climate Variability II
Friday, 28 March 2003, 8:30 AM-11:45 AM
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