Atlantic Coretop Foraminiferal Mg/Ca and d18O Calibration Data Arbuszewski, J.A.; deMenocal, P.B.; Kaplan, A.; Farmer, E.C. Arbuszewski, J.A. deMenocal, P.B. Kaplan, A. Farmer, E.C. earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean (VM29-178>LATITUDE 42.85>LONGITUDE -25.15) Paired foraminiferal Magnesium/Calcium ratio and oxygen isotope analyses are widely used to estimate surface ocean d18Oseawater, a robust proxy for surface salinity. We assess the fidelity of shell-derived d18Oseawater 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 d18Oseawater values are well correlated (r2=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", is highly correlated with surface salinity (r2=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 (r2=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 (< 35) 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 d18Oseawater estimates in high salinity settings (>35). STUDY NOTES: Coretop foraminiferal magnesium/calcium ratio and oxygen isotope data from a meridional transect of 64 Atlantic samples. Mg/Ca ratio and d18O measured on Globigerinoides ruber (white) are used to evaluate shell-derived d18Oseawater estimates across different salinity regimes in the Atlantic Ocean. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Arbuszewski, J.A. Investigator : deMenocal, P.B. Investigator : Kaplan, A. Investigator : Farmer, E.C. 2011-01-26 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/10513 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/arbuszewski2010/arbuszewski2010.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/arbuszewski2010/arbuszewski2010.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/arbuszewski2010/arbuszewski2010.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/arbuszewski2010/arbuszewski2010.xls English https://www.ncdc.noaa.gov/paleo/study/10513 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/arbuszewski2010/arbuszewski2010.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/arbuszewski2010/arbuszewski2010.xls Arbuszewski, J., P. deMenocal, A. Kaplan, and E.C. Farmer. 2010. On the fidelity of shell-derived d18Oseawater estimates. Earth and Planetary Science Letters, Vol. 300, Issues 3-4, pp. 185-196, 1 December 2010. doi:10.1016/j.epsl.2010.10.035 START YEAR: 10 cal yr BP * END YEAR: -10 cal yr BP -25.15 42.85 -25.15 42.85