The Influence of the Antarctic Circumpolar Wave upon Interannual Climate Variability in the Indian and Western Pacific Oceans.
Warren White, Scripps Institution of Oceanography. La Jolla, CA, USA
Rob Allan, CSIRO, Aspendale, Australia.
The Antarctic Circumpolar Wave (ACW) is a climate signal of nominal 4-year period in the ocean-atmosphere system in the Southern Ocean (40｡ to 70｡S), propagating eastward at an average speed of approximately 8 cm/sec, composed of two waves taking approximately 8 years to circle the globe (White and Peterson, 1996). The ACW is characterized by a persistent in-phase relationship between warm (cool) sea surface temperature (SST) anomalies and poleward (equatorward) meridional surface wind (MSW) anomalies. When the ACW propagagates eastward into the region south of Africa, portions of the covarying SST and MSW anomalies branch advectively northward into the South Atlantic and Indian oceans, taking 1 to 2 years to propagate in to the tropics in each basin. In the Indian ocean this north branch of the ACW influences the eastward propagation of covarying SST and SLP anomalies in the tropical Indo-Pacific, called the global ENSO wave by White and Cayan (2000) because of its ability to propagate across the tropical Indian, Pacific, and Atlantic ocean over a 4 to 6 year period. The eastward propagation of the global ENSO wave in the tropics and the ACW in the high latitudes appear to be independent, but this remains to be examined in greater detail. The propagation of the ACW past Australia, both on the west in the Indian ocean and on the south in the Southern Ocean has a major impact on year-to-year change in precipitation over Australia. and allows the latter to be predicted from one year to the next.
