Ocean Science

Correcting for Dissolute Behavior

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Science  04 Oct 2002:
Vol. 298, Issue 5591, pp. 15
DOI: 10.1126/science.298.5591.15d

Reconstructions of tropical sea surface temperature (SST) have indicated that tropical SSTs were colder by about 2° to 6°C during the Last Glacial Maximum. How much of this range reflects true oceanographic variability and how much is attributable to inaccuracies associated with different paleotemperature proxies is a topic of considerable controversy. The Mg/Ca of planktonic foraminifera is an increasingly popular proxy for SST, but foraminiferal Mg/Ca is susceptible to postdepositional alteration by dissolution on the seafloor, which can introduce relatively large uncertainties in calculated temperatures and across different temperature calibrations. Rosenthal and Lohmann describe a calibration for Mg/Ca paleothermometry in which size-normalized shell weight is used to correct for postdepositional dissolution of the forams. This approach improves the accuracy of SST estimates and is globally applicable. Using this correction, they calculate that the SST of the eastern equatorial Atlantic was 2.9° ± 0.4°C colder during the Last Glacial Maximum than today. — HJS

Paleoceanography17, 1044 (2002).

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