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A mid-twentieth century reduction in tropical upwelling inferred from coralline trace element proxies |
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| Authors: | Matthew K Reuer Edward A Boyle Julia E Cole |
| Institution: | a MIT/WHOI Joint Program in Oceanography, E34-200, Massachusetts Institute of Technology, Cambridge, MA 02139, USA b Department of Earth, Atmospheric, and Planetary Sciences, E34-200, Massachusetts Institute of Technology, Cambridge, MA 02139, USA c Department of Geosciences, The University of Arizona, Gould-Simpson Building, 1040 E. Fourth Street, Tucson, AZ 85721-0077, USA |
| Abstract: | The Cariaco Basin is an important archive of past climate variability given its response to inter- and extratropical climate forcing and the accumulation of annually laminated sediments within an anoxic water column. This study presents high-resolution surface coral trace element records (Montastrea annularis and Siderastrea siderea) from Isla Tortuga, Venezuela, located within the upwelling center of this region. A two-fold reduction in Cd/Ca ratios (3.5–1.7 nmol/mol) is observed from 1946 to 1952 with no concurrent shift in Ba/Ca ratios. This reduction agrees with the hydrographic distribution of dissolved cadmium and barium and their expected response to upwelling. Significant anthropogenic variability is also observed from Pb/Ca analysis, observing three lead maxima since 1920. Kinetic control of trace element ratios is inferred from an interspecies comparison of Cd/Ca and Ba/Ca ratios (consistent with the Sr/Ca kinetic artifact), but these artifacts are smaller than the environmental signal and do not explain the Cd/Ca transition. The trace element records agree with historical climate data and differ from sedimentary faunal abundance records, suggesting a linear response to North Atlantic extratropical forcing cannot account for the observed historical variability in this region. |
| Keywords: | trace elements Cariaco Basin coral reefs paleoclimatology cadmium barium |
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