HIGH-RESOLUTION RECORDS OF TROPICAL ATLANTIC CLIMATE VARIABILITY FROM THE CARIACO BASIN

The high-deposition rate laminated sediments of the Cariaco Basin make it perhaps the best available recorder of interannual- to century-scale climate variability for the tropical Atlantic. The ability to construct paleoenvironmental time-series with near-annual resolution in the most recently deposited of these sediments allows for calibration to historical instrumental records, and extrapolation into the past. Here we present results of high-resolution analyses of box and gravity core sediments that provide records of trade wind and Intertropical Convergence Zone (ITCZ) variability, sea surface temperatures (SST), and local upwelling intensity that span approximately the last 2000 years.

Continuous sampling of well-dated box and gravity core sediments at consecutive 1-mm intervals provides a record with a temporal resolution of 1-3 yrs for the time period ca. 1 to 1990 AD. G. bulloides abundance, previously shown to be an indicator of Atlantic trade wind intensity and SST in the northern North Atlantic, also correlates well with paleoclimate records from Africa and central North America between ~1250 and 1990 AD. A major shift in the population data of several Cariaco Basin species during the mid-1200's may indicate a significant change in the average annual position of the ITCZ, which in turn appears to change the relationships observed between the Cariaco Basin and other regional patterns of climate variability.

Stable oxygen isotope data generated on G. bulloides and G. ruber exhibit a strong negative correlation with Caribbean and tropical Atlantic SSTs for the period 1950-1990 AD, suggesting that these species potentially record and preserve seasonal SSTs in the sediment record. However, correlations with instrumental SSTs prior to 1950 are positive, indicating that the long-term relationship between Cariaco Basin planktonic foraminiferal stable oxygen isotope values and tropical Atlantic SSTs is more complicated than initially believed.