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Monthly Strontium/Calcium oscillations in symbiotic coral aragonite: Biological effects limiting the precision of the paleotemperature proxy
Geological and Environmental Sciences, Stanford University, USA
Danish Geotechnical Institute, Denmark
United States Geological Survey, USA
Biomechanical Engineering Division, Stanford University, USA
Geological and Environmental Sciences, Stanford University, USA
Department of Statistics, Stanford University, USA
Geological and Environmental Sciences, Stanford University, USA
United States Geological Survey, USA
Geological and Environmental Sciences, Stanford University, USA
In thermodynamic equilibrium with sea water the Sr/Ca ratio of aragonite varies predictably with temperature and the Sr/Ca ratio in coral have thus become a frequently used proxy for past Sea Surface Temperature (SST). However, biological effects can offset the Sr/Ca ratio from its equilibrium value. We report high spatial resolution ion microprobe analyses of well defined skeletal elements in the reef-building coral Porites lutea that reveal distinct monthly oscillations in the Sr/Ca ratio, with an amplitude in excess of ten percent. The extreme Sr/Ca variations, which we propose result from metabolic changes synchronous with the lunar cycle, introduce variability in Sr/Ca measurements based on conventional sampling techniques well beyond the analytical precision. These variations can limit the accuracy of Sr/Ca paleothermometry by conventional sampling techniques to about 2°C. Our results may help explain the notorious difficulties involved in obtaining an accurate and consistent calibration of the Sr/Ca vs. SST relationship.
Published 15 April 2003.
Citation: (2003), Monthly Strontium/Calcium oscillations in symbiotic coral aragonite: Biological effects limiting the precision of the paleotemperature proxy, Geophys. Res. Lett., 30(7), 1418, doi:10.1029/2002GL016864.
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