Persistent decadal-scale rainfall variability in the tropical South Pacific Convergence Zone through the past six centuries Etude des sites anciens d'Europe du Sud View project Persistent decadal-scale rainfall variability in the tropical South Pacific Convergence Zone through the past six centuries

Abstract

Modern Pacific decadal variability (PDV) has global impacts; hence records of PDV from the pre-instrumental period are needed to better inform models that are used to project future climate variability. We focus here on reconstructing rainfall in the western tropical Pacific (Solomon Islands; ∼ 9.5 • S, ∼ 160 • E), a region directly influenced by PDV, using cave deposits (stalagmite). A relationship is developed between δ 18 O variations in the stalagmite and local rainfall amount to produce a 600 yr record of rainfall variability from the South Pacific Convergence Zone (SPCZ). We present evidence for large (∼ 1.5 m), abrupt, and periodic changes in total annual rainfall amount on decadal to multidecadal timescales since 1423 ± 5 CE (Com-mon Era) in the Solomon Islands. The timing of the decadal changes in rainfall inferred from the 20th-century portion of the stalagmite δ 18 O record coincides with previously identified decadal shifts in PDV-related Pacific ocean-atmosphere behavior (Clement et al., 2011; Deser et al., 2004). The Solomons record of PDV is not associated with variations in external forcings, but rather results from internal climate variability. The 600 yr Solomon Islands stalagmite δ 18 O record indicates that decadal oscillations in rainfall are a persistent characteristic of SPCZ-related climate variability.