Decadal- to interannual-scale source water variations in the Caribbean Sea recorded by Puerto Rican coral radiocarbon |
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| Authors: | K Halimeda Kilbourne Terrence M Quinn Thomas P Guilderson Robert S Webb Frederick W Taylor |
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| Institution: | (1) College of Marine Science, University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33707, USA;(2) Institute for Geophysics, The John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin, 4412 Spicewood Springs Road, Austin, TX 78759-8500, USA;(3) Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, L-397, P.O. Box 808, Livermore, CA 94550, USA;(4) Department of Ocean Sciences and Institute of Marine Science, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA;(5) NOAA, Earth System Research Laboratory, R/PSD1, 325 Broadway, Boulder, CO 80305, USA |
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| Abstract: | Water that forms the Florida Current, and eventually the Gulf Stream, coalesces in the Caribbean from both subtropical and
equatorial sources. The equatorial sources are made up of, in part, South Atlantic water moving northward and compensating
for southward flow at depth related to meridional overturning circulation. Subtropical surface water contains relatively high
amounts of radiocarbon (14C), whereas equatorial waters are influenced by the upwelling of low 14C water and have relatively low concentrations of 14C. We use a 250 year record of Δ14C in a coral from southwestern Puerto Rico along with previously published coral Δ14C records as tracers of subtropical and equatorial water mixing in the northern Caribbean. Data generated in this study and
from other studies indicate that the influence of either of the two water masses can change considerably on interannual to
interdecadal time scales. Variability due to ocean dynamics in this region is large relative to variability caused by atmospheric
14C changes, thus masking the Suess effect at this site. A mixing model produced using coral Δ14C illustrates the time varying proportion of equatorial versus subtropical waters in the northern Caribbean between 1963 and
1983. The results of the model are consistent with linkages between multidecadal thermal variability in the North Atlantic
and meridional overturning circulation. Ekman transport changes related to tradewind variability are proposed as a possible
mechanism to explain the observed switches between relatively low and high Δ14C values in the coral radiocarbon records. |
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