ENSO history recorded in Agathis australis (kauri) tree rings. Part A: kauri's potential as an ENSO proxy.

Abstract

Although many of the main characteristics of the El Ni˜no-Southern Oscillation (ENSO) phenomenon have been established, uncertainties remain concerning its multidecadal- to millennial-scale evolution. Because of the shortness of the instrumental record, we need to resort to proxy-based reconstructions to investigate ENSO’s history prior to the mid 19th century, but the available proxy data is limited in both time and space. Here we investigate the potential for ENSO reconstruction from the tree rings of Agathis australis (kauri). Kauri is a long-lived endemic New Zealand conifer and grows in an ENSO teleconnection region not previously represented in ENSO multi-proxy studies. A high quality 423 year kauri regional master chronology (AD 1580–2002) is constructed. Statistical analysis of the period AD 1876–2002 confirms previous findings that kauri tree rings carry a strong regional-scale climate signal and that ENSO is a significant contributor (predominantly via the western pole of the Southern Oscillation). Kauri carries a signal of both ENSO phases, but with a slight El Ni˜no bias. Growth sensitivity is primarily registered through a five-season window, extending from March (prior to growth initiation in September) through to the following May, with strongest relationships across the middle three seasons (June–February). Relationships appear to be stationary. We conclude that kauri has sufficient ENSO event capture skill to make it a useful addition to future multi-proxy ENSO reconstruction efforts. It may also have potential for stand-alone reconstruction of multidecadal- to millennial-scale evolution of ENSO activity, especially ENSO robustness. Copyright  2007 Royal Meteorological Society