Reconstructing precipitation in the tropical South Pacific from dinosterol H-2/H-1 ratios in lake sediment

Maloney, Ashley E. and Nelson, Daniel B. and Riche, Julie N. and Prebble, Matthew and Sear, David A. and Hassall, Jonathan D. and Langdon, Peter G. and Croudace, Ian W. and Zawadzki, Atun and Sachs, Julian P.. (2019) Reconstructing precipitation in the tropical South Pacific from dinosterol H-2/H-1 ratios in lake sediment. Geochimica et Cosmochimica Acta, 245. pp. 190-206.

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Official URL: https://edoc.unibas.ch/74350/

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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). delta H-2(lakewater) values from 29 lakes ranged from -29 to +23 parts per thousand 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. .delta H-2(lakewater) values of the dinoflagellate sterol dinosterol in surficial sediments from 21 lakes ranged from -316 parts per thousand in the Solomon Islands to -245 parts per thousand in French Polynesia. These delta H-2(dimosterol) values were significantly correlated (r = 0.71, p < 0.001) with delta H-2(lakewater) and inversely correlated (r = -0.77, p < 0.001) with mean annual precipitation rates with a sensitivity of -12.1 +/- 2.6 parts per thousand (mm d(-1))(-1). Fractionation between dinosterol and lake water (epsilon(dinosterol/lakewater)) decreased at the driest lake sites (r = - 0.70, p < 0.001). The empirical relationship bet ween delta H-2(dmosterol) 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 which compares favorably to the 1.5 mm d(-1) uncertainty for the satellite-gauge based GPCP precipitation data.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Integrative Biologie > Physiological Plant Ecology (Kahmen)
UniBasel Contributors:Nelson, Daniel
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:17 Nov 2020 15:17
Deposited On:27 May 2020 09:59

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