Stable Isotope Record of El Niño-Southern Oscillation Events from Easter Island

Abstract

Easter Island (also known as Rapa Nui and Isla Pascua) lies within the southeastern Pacific high-pressure system, a feature that along with the Indonesian Low comprises the atmospheric dipole that defines the Southern Oscillation. Sea surface temperatures (SST) in the southeastern Pacific influence this limb of the basin-wide Walker circulation by modulating the stability and magnitude of convection within the regionally descending air. El Nino-Southern Oscillation (ENSO) research has most often focused on variability in the intensity and location of the Indonesian Low convective system or on teleconnections to various parts of the Northern Hemisphere. Long climate records from Easter Island will help elucidate the influence of oceanic variability on the overall ENSO system and its South Pacific teleconnections via the Walker Circulation. In addition, the Easter Island region of the South Pacific Gyre is a source for the shallow subsurface meridional flow that eventually upwells along the equator in the central and eastern Pacific [(Fig. 1); Levitus, 1982; Ji, et al., 1995; Gu and Philander, 1997]. In the northern Pacific, subsurface meridional flow has been suggested as a cause of decade-scale climate anomalies (Gu and Philander, 1997; Zhang et al, 1998). A similar mechanism may operate in the Southern Hemisphere; however, our current lack of a long time series of oceanic climate data from the eastern South Pacific Gyre, limits our ability to study this phenomenon.