GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 104-13
Presentation Time: 11:30 AM


MONTEAGUDO, Minda M.1, WELDEAB, Syee1, LEA, David W.1, ROSENTHAL, Yair2 and KARL, David M.3, (1)Department of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106, (2)Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901, (3)Department of Oceanography and Daniel K. Inouye Center for Microbial Ecology: Research and Education, University of Hawaii, Manoa, Honolulu, HI 96822,

Planktonic foraminiferal Mg/Ca is one of the most widely-applied proxies for sea surface temperature reconstructions. Current calibrations yield a temperature sensitivity of 9.0 ± 1.0% Mg/Ca per °C (1-2). Recent studies suggest, however, that these estimates may be additionally influenced by salinity. Culture experiments suggest 3.3±1.7% increase in Mg/Ca per salinity unit (3), substantially lower than controversial evidence of 27±4% (4).

Here we present a paired Mg/Ca and δ18O study in Globigerinoides ruber (sensu lato, 250-350µm) from sediment trap samples from the Hawaii Ocean Time Series. Within the habitat depth range of G. ruber(0-25 m), seasonal temperature and salinity vary by 4 °C and 0.7 practical salinity units, respectively. The relatively small seasonal changes in salinity allow us to isolate and quantify the temperature effect on Mg/Ca using spatially and temporally high-resolved temperature measurements. Our study shows an exponential Mg/Ca-temperature relationship of:

Mg/Ca [mmol/mol] = (0.92 ± 0.35)exp((0.065 ± 0.015)*T[˚C]) (RMSE=0.31).

Multivariate regression incorporating both temperature and salinity does not reveal a significant salinity influence on our data; the temperature sensitivity of the multivariate fit agrees within error with the above (T-only) equation. Our results indicate a temperature sensitivity of 6.5 ± 1.5% Mg/Ca per °C that is in agreement, within error, with the results of a culture-based study that accounts for salinity effect (5), supporting the emerging notion that the temperature influence on Mg/Ca may be lower than the canonical 9% per °C value (1-2).

1. Anand et al., Paleoceanography, 18, 1050 (2003); 2. Dekens et al., G3 3, 1022 (2002); 3. Hönisch et al., GCA, 121, 196-213 (2013); 4. J. Arbuszewski et al., EPSL, 300, 185-196 (2010); 5. Kisakürek et al., EPSL, 273, 260–269 (2008).