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A novel salinity proxy based on Na incorporation into foraminiferal calcite

Wolthers, MVH; Wit, JC; de Nooijer, LJ; Reichart, GJ; (2013) A novel salinity proxy based on Na incorporation into foraminiferal calcite. Biogeosciences Discussions , 10 (3) pp. 6039-6063. 10.5194/bgd-10-6039-2013. Green open access

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Abstract

Salinity and temperature determine seawater density, and differences in both thereby control global thermohaline circulation. Whereas numerous proxies have been calibrated and applied to reconstruct temperature, a direct and independent proxy for salinity is still missing. Ideally, a new proxy for salinity should target one of the direct constituents of dissolved salt, such as [Na+] or [Cl−]. This study investigates the impact of salinity on foraminiferal Na/Ca values by laser ablation ICP-MS analyses of specimens of the benthic foraminifer Ammonia tepida cultured at a range of salinities (30.0–38.6). Foraminifera at lower salinities (30.0 and 32.5) added more chambers (10–11) to their test over the course of the culturing experiment than those maintained at higher salinities (36.1, 7–8 chambers, and 38.6, 6–7 chambers), suggesting that growth rates in this species are promoted by lower salinities. The Na/Ca of cultured specimens correlates significantly with seawater salinity (Na/Ca = 0.22S–0.75, R2 = 0.96, p < 0.01) and size. Values for Na/Ca and DNa vary between 5.17 and 9.29 mmol mol−1 and 0.12–0.16 × 10−3, which are similar to values from inorganic precipitation experiments. The significant correlation between test size and Na/Ca results from co-variation with salinity. This implies that foraminiferal Na/Ca could serve as a robust and independent proxy for salinity, enabling salinity reconstructions independent of calcitic δ18O.

Type: Article
Title: A novel salinity proxy based on Na incorporation into foraminiferal calcite
Open access status: An open access version is available from UCL Discovery
DOI: 10.5194/bgd-10-6039-2013
Publisher version: http://dx.doi.org/10.5194/bgd-10-6039-2013
Language: English
Additional information: © Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 License.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1409337
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