Article

Climate Dynamics

, Volume 29, Issue 1, pp 51-62

Decadal- to interannual-scale source water variations in the Caribbean Sea recorded by Puerto Rican coral radiocarbon

  • K. Halimeda KilbourneAffiliated withCollege of Marine Science, University of South FloridaNOAA, Earth System Research Laboratory Email author 
  • , Terrence M. QuinnAffiliated withCollege of Marine Science, University of South FloridaInstitute for Geophysics, The John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin
  • , Thomas P. GuildersonAffiliated withCenter for Accelerator Mass Spectrometry, Lawrence Livermore National LaboratoryDepartment of Ocean Sciences and Institute of Marine Science, University of California at Santa Cruz
  • , Robert S. WebbAffiliated withNOAA, Earth System Research Laboratory
  • , Frederick W. TaylorAffiliated withInstitute for Geophysics, The John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin

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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.