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Coral Sr-U thermometry

Coral Sr-U thermometry
Coral Sr-U thermometry
Coral skeletons archive past climate variability with unrivaled temporal resolution. However, extraction of accurate temperature information from coral skeletons has been limited by “vital effects,” which confound, and sometimes override, the temperature dependence of geochemical proxies. We present a new approach to coral paleothermometry based on results of abiogenic precipitation experiments interpreted within a framework provided by a quantitative model of the coral biomineralization process. DeCarlo et al. (2015a) investigated temperature and carbonate chemistry controls on abiogenic partitioning of Sr/Ca and U/Ca between aragonite and seawater and modeled the sensitivity of skeletal composition to processes occurring at the site of calcification. The model predicts that temperature can be accurately reconstructed from coral skeleton by combining Sr/Ca and U/Ca ratios into a new proxy, which we refer to hereafter as the Sr-U thermometer. Here we test the model predictions with measured Sr/Ca and U/Ca ratios of 14 Porites sp. corals collected from the tropical Pacific Ocean and the Red Sea, with a subset also analyzed using the boron isotope (?11B) pH proxy. Observed relationships among Sr/Ca, U/Ca, and ?11B agree with model predictions, indicating that the model accounts for the key features of the coral biomineralization process. By calibrating to instrumental temperature records, we show that Sr-U captures 93% of mean annual temperature variability (26–30°C) and has a standard deviation of prediction of 0.5°C, compared to 1°C using Sr/Ca alone. The Sr-U thermometer may offer significantly improved reliability for reconstructing past ocean temperatures from coral skeletons.
coral, paleoclimate, sea surface temperature, geochemistry, biomineralization
0883-8305
626-638
DeCarlo, Thomas M.
147ab85a-e040-432a-b2cb-224fe2d838df
Gaetani, Glenn A.
401ce2f7-3621-4322-b666-84f377361322
Cohen, Anne L.
b20be412-6349-4bc6-85c1-e5d5a3aafdcf
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Alpert, Alice E.
2dc9d124-5037-4005-aa93-37174dfe413b
Stewart, Joseph A.
69894bea-c03d-44a9-8f12-ff55580c6009
DeCarlo, Thomas M.
147ab85a-e040-432a-b2cb-224fe2d838df
Gaetani, Glenn A.
401ce2f7-3621-4322-b666-84f377361322
Cohen, Anne L.
b20be412-6349-4bc6-85c1-e5d5a3aafdcf
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Alpert, Alice E.
2dc9d124-5037-4005-aa93-37174dfe413b
Stewart, Joseph A.
69894bea-c03d-44a9-8f12-ff55580c6009

DeCarlo, Thomas M., Gaetani, Glenn A., Cohen, Anne L., Foster, Gavin L., Alpert, Alice E. and Stewart, Joseph A. (2016) Coral Sr-U thermometry. Paleoceanography, 31 (6), 626-638. (doi:10.1002/2015PA002908).

Record type: Article

Abstract

Coral skeletons archive past climate variability with unrivaled temporal resolution. However, extraction of accurate temperature information from coral skeletons has been limited by “vital effects,” which confound, and sometimes override, the temperature dependence of geochemical proxies. We present a new approach to coral paleothermometry based on results of abiogenic precipitation experiments interpreted within a framework provided by a quantitative model of the coral biomineralization process. DeCarlo et al. (2015a) investigated temperature and carbonate chemistry controls on abiogenic partitioning of Sr/Ca and U/Ca between aragonite and seawater and modeled the sensitivity of skeletal composition to processes occurring at the site of calcification. The model predicts that temperature can be accurately reconstructed from coral skeleton by combining Sr/Ca and U/Ca ratios into a new proxy, which we refer to hereafter as the Sr-U thermometer. Here we test the model predictions with measured Sr/Ca and U/Ca ratios of 14 Porites sp. corals collected from the tropical Pacific Ocean and the Red Sea, with a subset also analyzed using the boron isotope (?11B) pH proxy. Observed relationships among Sr/Ca, U/Ca, and ?11B agree with model predictions, indicating that the model accounts for the key features of the coral biomineralization process. By calibrating to instrumental temperature records, we show that Sr-U captures 93% of mean annual temperature variability (26–30°C) and has a standard deviation of prediction of 0.5°C, compared to 1°C using Sr/Ca alone. The Sr-U thermometer may offer significantly improved reliability for reconstructing past ocean temperatures from coral skeletons.

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Coral_Sr-U_Thermometry_accepted.pdf - Accepted Manuscript
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More information

Accepted/In Press date: 12 May 2016
e-pub ahead of print date: 11 June 2016
Published date: June 2016
Keywords: coral, paleoclimate, sea surface temperature, geochemistry, biomineralization
Organisations: Geochemistry

Identifiers

Local EPrints ID: 397097
URI: https://eprints.soton.ac.uk/id/eprint/397097
ISSN: 0883-8305
PURE UUID: 07f7196b-1c2c-4734-9351-65cb6532c32f
ORCID for Gavin L. Foster: ORCID iD orcid.org/0000-0003-3688-9668

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Date deposited: 20 Jun 2016 16:09
Last modified: 03 Dec 2019 01:42

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