Abstract
The South Pacific Convergence Zone (SPCZ) is the Southern Hemisphere's largest precipitation feature supplying freshwater to 11 million people. Despite its significance, little is known about the location and intensity of SPCZ precipitation prior to instrumental records, hindering attempts to predict precipitation changes in a warming world. Here we use sedimentary molecular fossils to establish a tool for extending the historical record of precipitation. Freshwater lake sediments and water samples were collected from 30 lakes that span a 4.6 mm d−1 range in precipitation rates from the Global Precipitation Climatology Project (GPCP). δ2Hlakewater values from 29 lakes ranged from −29 to +23‰ and were inversely correlated (r = −0.51, p < 0.001) with precipitation rates, likely due to the combination of the amount of precipitation plus evaporation. δ2H values of the dinoflagellate sterol dinosterol in surficial sediments from 21 lakes ranged from −316‰ in the Solomon Islands to −245‰ in French Polynesia. These δ2Hdinosterol values were significantly correlated (r = 0.71, p < 0.001) with δ2Hlakewater and inversely correlated (r = −0.77, p < 0.001) with mean annual precipitation rates with a sensitivity of −12.1 ± 2.6‰ (mm d−1)−1. Fractionation between dinosterol and lake water (εdinosterol/lakewater) decreased at the driest lake sites (r = − 0.70, p < 0.001). The empirical relationship between δ2Hdinosterol and GPCP rainfall, although indirect, provides a means of quantitatively reconstructing past precipitation in the SPCZ region with an uncertainty of less than 3.1 mm d−1, which compares favorably to the 1.5 mm d−1 uncertainty for the satellite-gauge based GPCP precipitation data.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 190-206 |
| Number of pages | 17 |
| Journal | Geochimica et Cosmochimica Acta |
| Volume | 245 |
| DOIs | |
| State | Published - Jan 15 2019 |
Bibliographical note
Funding Information:This material is based upon work supported by the US National Science Foundation under Grant Nos. 0823503 and 1502417 to J.P.S; a University of Washington Program on Climate Change Fellowship and IGERT Ocean Change Fellowship [grant #NSF1068839 ] provided partial support for A.E.M; radiometric dating was supported by AINSE (The Australian Institute of Nuclear Science and Engineering) [Award No ALNGRA14513 and ALNGRA16012 ] to M.P.; IGERT Ocean Change mini-research awards, and a University of Washington Quaternary Research Center research award to A.E.M. The James and Marsha Seeley Foundation and the Tetiaroa Society supported the research on Tetiaroa; The Explorers Club Exploration Fund Grant, Gilchrist Expedition Grant and Royal Geographical Society (with IBG) Monica Cole Grant assisted with travel to Samoa. Funding was provided for Lake Emoatul (2015 & 2017 visit) through NERC Urgent grant NE/N006674/1 . Lake Lanoto’o and New Caledonia data was funded under a NERC Studentship to J.D.H.. All radioisotope dating for lake Emoatul and Lanoto’o were undertaken by GAU. The authors would like to thank G. Hope for providing sediment from his 1995 visit to Lake Emaotul and Bren Weatherstone for assistance with sample collection, S. Haberle for providing sediment from his 1998 visit to Lake Wanum, and R. Smittenberg for extracting lipids from the Lake Wanum sample. We are grateful for permission from Wallis Island civic and traditional authorities. Sample collection on Wallis Island benefitted from the assistance of U. Sichrowsky, J.-Y. Meyer, A. Malau, K. Manufeki, S. Tauvale, C. Manry and others from Service de L’Environment, M. Fotuaika, J.-F. Poncet, P. Nicomette, S. Felomaki, P. Tauvale, C. Chauvet, and the planning assistance from R. Schabetsberger, C. Lique, M. Bridoux, and C. Altman. We would like to thank T. Thomas and the Tetepare Descendants’ Association Rangers for helping with sample collection in the Solomon Islands. We thank Cerillo Balo from the Vanuatu Kaljarol Senta at Port Olry for assisting with sample collection in Vanuatu (2012). In Vanuatu (2015 & 2017) we would like to thank Esline Garaebiti and Philip Malsale of the Geo-Hazards Division, Government of Vanuatu for permission to undertake fieldwork in Efate, Lake Emoatul, and to Fabienne, Maurice and Hugo for assistance with construction of the coring platform. Thanks to Msr. François Le Borgne and the Department of Pollution Prevention and Risk, New Caledonia for permission to core Grand Lac and Lake Hut and to Olivier for field assistance. Field work in Upolu, Samoa was kindly permitted by Taule’ale’ausmai Laavasa Malua, Chief Executive Officer, Niualuga Evaimalo and staff in Ministry Natural Resources and Environment. Field assistance was provided by Josie Hill, Lucy, Tinifu, Solomano and Ai. We are grateful to the Tetiaroa Society and the government of French Polynesia for permission to collect samples from Tetiaroa, and for the assistance of the Tetiaroa Society, C. Saenger, I. Bolden, A. Gagnon, J. Gregersen, and L. Brandkamp in collecting those samples. S. Hing, E. Baldwin, A. Witt, and P Sobeck provided careful assistance in the lab. M. Wolfshorndl, T. Magee, S. N. Ladd, J. Rodysill, and K. Brady assisted with splitting cores at LacCore. We thank Melenie Leng for analyzing New Caledonia and Samoa water isotope samples from Samoa and New Caledonia undertaken at the NERC Isotope Geosciences Laboratory. We thank C. Kaapu-Lyons, N. Wallsgrove, and B. Popp for analyzing Wallis Island water samples. We thank Flett Research Ltd. for performing 210 Pb analysis and also Jack Goralewski, Brodie Cutmore, and Daniela Fierro for performing 210 Pb analysis at ANSTO. Conversations with L. Thompson, S. PoChedley, R. Echols, J. Scheff, S. Rushley, D. Battisti, R. Wood, K. Thirumalai and constructive comments from A.E. Ingalls, P. Quay, and J.A. Flannery greatly improved this manuscript. Finally, we would like to thank two anonymous reviewers and Associate Editor Jochen Brocks for helpful comments and suggestions that improved this manuscript.
Publisher Copyright:
© 2018 Elsevier Ltd
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
Keywords
- Dinosterol
- Evaporation
- Hydrogen isotopes
- Lake sediment
- Organic geochemistry
- Paleoclimatology
- Precipitation
- South Pacific Convergence Zone
- Tropical Pacific
Continental Scientific Drilling Facility tags
- SPCZ14
