COUPLED HYDROGRAPHIC AND TROPICAL CYCLONE VARIABILITY IN THE SOUTH PACIFIC OVER THE LATE HOLOCENE

Movement of the South Pacific Convergence Zone (SPCZ) drives major changes in rainfall and tropical cyclone activity across the central South Pacific. Some of the strongest SPCZ driven precipitation variability is seen in French Polynesia, but it has few conventional sites (e.g., upland lakes) that may be used for multi-millennial proxy rainfall records, greatly limiting our ability to understand how tropical Pacific climate has changed in the past. Here we use a high-resolution proxy runoff record from Apu Bay on the island of Tahaa, French Polynesia, to document changes in precipitation, inferred to reflect SPCZ variability, in the central South Pacific since 2250 yrs BP. Changes in precession (millennial-scale) and global temperature (centennial-scale) best explain evidence of a coordinated pattern of rainfall variability at Tahaa and across the Pacific over the late-Holocene. A companion record of tropical cyclone activity from Tahaa, along with a compilation of storm-derived deposits from across the basin, suggests major storm activity was much higher between 2060-1250 yrs BP, when rainfall was low, in contrast with modern climatology. Observed changes in storminess and hydroclimate are also concurrent with migration by early Polynesians into the central Pacific and our data provide further support that climatic variability may have aided their expansion.