On the fidelity of shell-derived δ18Oseawater estimates

Autor: Peter B deMenocal, E. Christa Farmer, J. A. Arbuszewski, Alexey Kaplan
Rok vydání: 2010
Předmět:
Zdroj: Earth and Planetary Science Letters. 300:185-196
ISSN: 0012-821X
DOI: 10.1016/j.epsl.2010.10.035
Popis: article i nfo 18 Oseawater,a robustproxyforsurfacesalinity.We assessthe fidelity of shell-derived δ 18 Oseawater estimates for the surface-dwelling foraminifer Globigerinoides ruber (white) using an Atlantic meridional coretop transect spanning basin-scale temperature and salinity gradients. Shell-derived and observed δ 18 Oseawater values are well correlated (r 2 =0.77), but a large systematic bias is observed. Shell Mg/Ca ratios are significantly elevated above values expected from observed and isotopic calcification temperatures in the saline subtropical gyres of both hemispheres. This temperature-independent shell Mg/Ca ratio variability, termed "excess Mg/Ca" ,i s highly correlated with surface salinity (r 2 =0.77), and the observed salinity dependence (27±4%) is much higher than indicated by culture studies (6±2%). Our coretop data are used to develop new Atlantic Basin temperature and salinity calibration equations that are accurate (±1.1 °C and ±0.20, respectively), precise (r 2 =0.82 and 0.81, respectively), and verifiable using previously published data. These results are valid for the relatively high salinities of the subtropical Atlantic (35.5-37.3). We discover that inclusion of other published data from lower salinity regions (b35) indicates little or no excess Mg/Ca. Taken together, these results point to a strongly non-linear, positive salinity effect on shell Mg/Ca ratios that significantly affects the accuracy of SST and δ 18
Databáze: OpenAIRE
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