Graduation Year

2006

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Marine Science

Major Professor

Terrence M. Quinn, Ph.D.

Keywords

Coral, Oxygen isotope, Stontium, Radiocarbon, Little ice age

Abstract

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 global 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]. A theme of past Caribbean paleoclimate research has been to hypothesize about the interaction between mean climate state and seasonality, but little work has actually been done with sub-annually resolved climate proxies, and many questions still remain unanswered.

This work focuses on reconstructing ocean conditions in the northern Caribbean from the geochemistry of corals growing offshore of southwestern Puerto Rico (17.9°N, 67.0°W). Annually resolved records of Sr/Ca and δ18O were generated for the years 2004 to 1751 from one continuous core. The same annual samples were analyzed for Î?14C between 2004 and 1950, and every 5 years between 1955-1751. Short (14-4 years) monthly-resolved records of δ18O and Sr/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 delta-18-O and Delta-14-C was found to correlate temporally with the intensity of the trade winds during recent times and over the last 250 years.

Strong trade winds are associated with isotopic depletion in the coral geochemistry with respect to both 18-O and 14-C, 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 2 degree C cooling in the Caribbean during the Maunder solar minimum and no change in coral delta-18-O 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 delta-18-O in corals growing on the same reef at the same time is 0.047 mmol/mol and 0.11 permil, respectively.

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