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

Reconstructing precipitation in the tropical South Pacific from dinosterol 2H/1H ratios in lake sediment
Reconstructing precipitation in the tropical South Pacific from dinosterol 2H/1H ratios in lake sediment
The South Pacific Convergence Zone (SPCZ) is the largest precipitation feature in the Southern Hemisphere 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). 2Hlakewater values from 29 lakes ranged from –29 to +23‰ and were inversely correlated (r= −0.51, R2=0.26, p<0.001) with precipitation rates, likely due to the combination of the amount of precipitation plus evaporation. 2H 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 2Hdinosterol values were significantly correlated (r= −0.71, R2=0.50, p<0.001) with 2Hlakewater and inversely correlated (r= −0.77, R2 =0.59, 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) increased at the wettest lake sites (R2=0.48, p<0.001). The empirical relationship between 2Hdinosterol 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.
0016-7037
190-206
Maloney, Ashley
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Nelson, Daniel
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Richey, Julie
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Prebble, Matt
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Sear, David
ccd892ab-a93d-4073-a11c-b8bca42ecfd3
Hassall, Jonathan
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Langdon, Peter
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Croudace, Ian
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Zawadzki, Atun
ac9e5e87-48b6-4e7b-9c05-285515e335f7
Sachs, Julian
d51899d1-5d92-4ca0-a0e8-c2e543a9fd46
Maloney, Ashley
aab6ca72-487c-441d-a52e-92329c4dc7a2
Nelson, Daniel
88bd1508-4612-470e-a610-a8e1866bb5ce
Richey, Julie
87742b2e-1e58-49a0-a1ce-456885f7a51e
Prebble, Matt
3e631d9b-7e25-4cf2-9098-b20f5a81e465
Sear, David
ccd892ab-a93d-4073-a11c-b8bca42ecfd3
Hassall, Jonathan
17b719cf-5b7b-496a-8bf7-96c57618baca
Langdon, Peter
95b97671-f9fe-4884-aca6-9aa3cd1a6d7f
Croudace, Ian
24deb068-d096-485e-8a23-a32b7a68afaf
Zawadzki, Atun
ac9e5e87-48b6-4e7b-9c05-285515e335f7
Sachs, Julian
d51899d1-5d92-4ca0-a0e8-c2e543a9fd46

Maloney, Ashley, Nelson, Daniel, Richey, Julie, Prebble, Matt, Sear, David, Hassall, Jonathan, Langdon, Peter, Croudace, Ian, Zawadzki, Atun and Sachs, Julian (2019) Reconstructing precipitation in the tropical South Pacific from dinosterol 2H/1H ratios in lake sediment. Geochimica et Cosmochimica Acta, 245, 190-206. (doi:10.1016/j.gca.2018.10.028).

Record type: Article

Abstract

The South Pacific Convergence Zone (SPCZ) is the largest precipitation feature in the Southern Hemisphere 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). 2Hlakewater values from 29 lakes ranged from –29 to +23‰ and were inversely correlated (r= −0.51, R2=0.26, p<0.001) with precipitation rates, likely due to the combination of the amount of precipitation plus evaporation. 2H 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 2Hdinosterol values were significantly correlated (r= −0.71, R2=0.50, p<0.001) with 2Hlakewater and inversely correlated (r= −0.77, R2 =0.59, 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) increased at the wettest lake sites (R2=0.48, p<0.001). The empirical relationship between 2Hdinosterol 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.

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Maloney SPCZ Coretop accepted - Accepted Manuscript
Restricted to Repository staff only until 3 November 2019.
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More information

Accepted/In Press date: 27 October 2018
e-pub ahead of print date: 3 November 2018
Published date: 15 January 2019

Identifiers

Local EPrints ID: 425749
URI: https://eprints.soton.ac.uk/id/eprint/425749
ISSN: 0016-7037
PURE UUID: 9774420d-2332-4ff1-ad44-66fd1b24a9ac
ORCID for David Sear: ORCID iD orcid.org/0000-0003-0191-6179
ORCID for Peter Langdon: ORCID iD orcid.org/0000-0003-2724-2643

Catalogue record

Date deposited: 02 Nov 2018 17:30
Last modified: 14 Mar 2019 01:52

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