PP13A-2260
Modern Spatial Rainfall Rate is well Correlated with Coretop δ2Hdinosterol in the South Pacific Convergence Zone: A Tool for Quantitative Reconstructions of Rainfall Rate

Monday, 14 December 2015
Poster Hall (Moscone South)
Ashley E Maloney1, Daniel B Nelson2, Julian P Sachs3, Jonathan D Hassall4, David Ayres Sear5, Peter G Langdon4 and Matthew Prebble6, (1)University of Washington Seattle Campus, Oceanography, Seattle, WA, United States, (2)University of Basel, Basel, Switzerland, (3)University of Washington Seattle Campus, Seattle, WA, United States, (4)University of Southampton, Southampton, United Kingdom, (5)University of Southampton, Southampton, SO14, United Kingdom, (6)Australian National University, Canberra, Australia
Abstract:
The South Pacific Convergence Zone (SPCZ) is the Southern Hemisphere’s most prominent precipitation feature extending southeastward 3000 km from Papua New Guinea to French Polynesia. Determining how the SPCZ responded to climate variations before the instrumental record requires the use of indirect indicators of rainfall. The link between the hydrogen isotopic composition of fluxes of water though the hydrologic cycle, lake water, and molecular fossil 2H/1H ratios make hydrogen isotopes a promising tool for improving our understanding of this important climate feature. An analysis of coretop sediment from freshwater lakes in the SPCZ region indicates that there is a strong spatial relationship between δ2Hdinosterol and mean annual precipitation rate. The objectives of this research are to use 2H/1H ratios of the biomarker dinosterol to develop an empirical relationship between δ2Hdinosterol and modern environmental rainfall rates so that we may quantitatively reconstruct several aspects of the SPCZ’s hydrological system during the late Holocene. The analysis includes lake sediment coretops from the Solomon Islands, Wallis Island, Vanuatu, Tahiti, Samoa, New Caledonia, and the Cook Islands. These islands span range of average modern precipitation rates from 3 to 7 mm/day and the coretop sediment δ2Hdinosterol values range from -240‰ to -320‰. Applying this regional coretop calibration to dated sediment cores reveals that the mean annual position and/or intensity of the SPCZ has not been static during the past 2000 years.