Global variability in seawater Mg:Ca and Sr:Ca ratios in the modern ocean

Lebrato, Mario, Garbe-Schönberg, Dieter, Müller, Marius N., Blanco-Ameijeiras, Sonia, Feely, Richard A., Lorenzoni, Laura, Molinero, Juan-Carlos, Bremer, Karen, Jones, Daniel O. B., Iglesias-Rodriguez, Debora, Greeley, Dana, Lamare, Miles D., Paulmier, Aurelien, Graco, Michelle, Cartes, Joan, Barcelos e Ramos, Joana, de Lara, Ana, Sanchez-Leal, Ricardo, Jimenez, Paz, Paparazzo, Flavio E., Hartman, Susan E., Westernströer, Ulrike, Küter, Marie, Benavides, Roberto, da Silva, Armindo F., Bell, Steven, Payne, Chris, Olafsdottir, Solveig, Robinson, Kelly, Jantunen, Liisa M., Korablev, Alexander, Webster, Richard J., Jones, Elizabeth M., Gilg, Olivier, Bailly du Bois, Pascal, Beldowski, Jacek, Ashjian, Carin, Yahia, Nejib D., Twining, Benjamin, Chen, Xue-Gang, Tseng, Li-Chun, Hwang, Jiang-Shiou, Dahms, Hans-Uwe and Oschlies, Andreas (2020) Global variability in seawater Mg:Ca and Sr:Ca ratios in the modern ocean PNAS Proceedings of the National Academy of Sciences of the United States of America, 117 (36). pp. 22281-22292. DOI 10.1073/pnas.1918943117.

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Supplementary data:

Abstract

Seawater Mg:Ca and Sr:Ca ratios are biogeochemical parameters reflecting the Earth-ocean-atmosphere dynamic exchange of elements. The ratios' dependence on the environment and organisms' biology facilitates their application in marine sciences. Here, we present a measured single-laboratory dataset, combined with previous data, to test the assumption of limited seawater Mg:Ca and Sr:Ca variability across marine environments globally. High variability was found in open-ocean upwelling and polar regions, shelves/neritic and river-influenced areas, where seawater Mg:Ca and Sr:Ca ratios range from ∼4.40 to 6.40 mmol:mol and ∼6.95 to 9.80 mmol:mol, respectively. Open-ocean seawater Mg:Ca is semiconservative (∼4.90 to 5.30 mol:mol), while Sr:Ca is more variable and nonconservative (∼7.70 to 8.80 mmol:mol); both ratios are nonconservative in coastal seas. Further, the Ca, Mg, and Sr elemental fluxes are connected to large total alkalinity deviations from International Association for the Physical Sciences of the Oceans (IAPSO) standard values. Because there is significant modern seawater Mg:Ca and Sr:Ca ratios variability across marine environments we cannot absolutely assume that fossil archives using taxa-specific proxies reflect true global seawater chemistry but rather taxa- and process-specific ecosystem variations, reflecting regional conditions. This variability could reconcile secular seawater Mg:Ca and Sr:Ca ratio reconstructions using different taxa and techniques by assuming an error of 1 to 1.50 mol:mol, and 1 to 1.90 mmol:mol, respectively. The modern ratios' variability is similar to the reconstructed rise over 20 Ma (Neogene Period), nurturing the question of seminonconservative behavior of Ca, Mg, and Sr over modern Earth geological history with an overlooked environmental effect.

Document Type: Article
Keywords: biogeochemistry; global; Mg:Ca; seawater; Sr:Ca
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
NOC
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-OEB Ökosystembiologie des Ozeans
Woods Hole
OceanRep > The Future Ocean - Cluster of Excellence
Kiel University
Refereed: Yes
DOI etc.: 10.1073/pnas.1918943117
ISSN: 0027-8424
Related URLs:
Projects: Future Ocean, EPOCA
Date Deposited: 21 Sep 2020 11:27
Last Modified: 21 Sep 2020 11:27
URI: http://eprints.uni-kiel.de/id/eprint/50558

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