Global variability in seawater Mg:Ca and Sr:Ca ratios in the modern ocean.
Proc Natl Acad Sci U S A
; 117(36): 22281-22292, 2020 09 08.
Article
em En
| MEDLINE
| ID: mdl-32843340
ABSTRACT
Seawater MgCa and SrCa 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 MgCa and SrCa variability across marine environments globally. High variability was found in open-ocean upwelling and polar regions, shelves/neritic and river-influenced areas, where seawater MgCa and SrCa ratios range from â¼4.40 to 6.40 mmolmol and â¼6.95 to 9.80 mmolmol, respectively. Open-ocean seawater MgCa is semiconservative (â¼4.90 to 5.30 molmol), while SrCa is more variable and nonconservative (â¼7.70 to 8.80 mmolmol); 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 MgCa and SrCa 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 MgCa and SrCa ratio reconstructions using different taxa and techniques by assuming an error of 1 to 1.50 molmol, and 1 to 1.90 mmolmol, 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.
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01-internacional
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MEDLINE
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Ano de publicação:
2020
Tipo de documento:
Article