Analysis of the influence of salinity on Mg/Ca ratios of cultured and coretop planktic foraminifers
Abstract
The Mg/Ca ratio in foraminiferal calcite is one of the most prominent proxies for paleoceanographic temperature reconstructions but recent coretop sediment observations have raised concerns that salinity may exert a significant (27% increase per salinity unit) secondary control on planktic foraminifers. Because multiple environmental variables can change simultaneously in the ocean, we have performed laboratory culture experiments with the planktic foraminifers Orbulina universa, Globigerinoides sacculifer and Globigerinoides ruber, where salinity was the only variable. In these experiments we find a Mg/Ca-sensitivity to salinity of less than 5% in all three species and thus conclude that the stronger effect observed in marine sediments cannot be thermodynamic. Rather, we hypothesize that the Mg/Ca and δ18O variations observed in Atlantic coretop sediments are likely due to either another environmental parameter or ecophysiological response that covaries with salinity. We evaluate the dissolution correction commonly applied to Mg/Ca-temperature estimates, and analyze the proxy records in the light of seasonal and vertical physico-chemical distribution patterns in the surface ocean.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.B21C0356H
- Keywords:
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- 0419 BIOGEOSCIENCES / Biomineralization;
- 1050 GEOCHEMISTRY / Marine geochemistry;
- 4924 PALEOCEANOGRAPHY / Geochemical tracers;
- 4954 PALEOCEANOGRAPHY / Sea surface temperature