The Caribbean Sea is a key region from which to generate paleoclimate records because instrumental temperature data indicate that surface temperatures in the Caribbean region are correlated with hemispheric surface temperature. Heat and salt fluxes in the Caribbean have been implicated in major reorganizations in Atlantic Meridional Overturning Circulation on glacial time scales [Schmidt et al., 2004] and it has been proposed that the Tropical Atlantic (including the Caribbean Sea) may play a role in smaller-scale changes in the Atlantic basin [Vellinga and Wu, 2004]. Previous work in the Northern Caribbean indicates that conditions were 2ûC cooler than today during the early 18th century. The data are somewhat controversial, in part because of the implications for the sensitivity of the climate system to climatic forcing. Confirmation of such large magnitude changes are needed.
This work focuses on reconstructing ocean conditions in the northern Caribbean from the geochemistry of corals growing offshore of southwestern Puerto Rico (17.9ûN, 67.0ûW). Annually resolved records of Sr/Ca and d18O were generated for the years 2004 to 1751 from one continuous core. The same annual samples were analyzed for D14C between 2004 and 1950, and every 5 years between 1955-1751. Short (14-4 years) monthly-resolved records of d18O and S/Ca were generated from this core and two other cores to investigate the role of seasonal variability during mean climate state variations.
Substantial multidecadal variability in d18O and D14C was found to correlate temporally with the intensity of the trade winds during recent times and over the last 250 years. Strong trade winds tend to cause isotopic depletion in the coral geochemistry with respect to both 18O and 14C, and this is interpreted as an increase in the amount of equatorial or southern Caribbean Sea water in the northern Caribbean. Other findings include a 2ûC cooling in the Caribbean during the Maunder solar minimum and no change in coral d18O seasonality during significant mean state variations. Inter-colony geochemical variability in the coral species Montastraea faveolata was quantified, and the median difference between Sr/Ca and d18O in corals growing on the same reef at the same time is 0.047 mmol/mol and 0.11 ä, respectively.