Extracting a climate signal from the skeletal geochemistry of the Caribbean coral Siderastrea siderea

Abstract

The first bimonthly time series of paired δ18O and Sr/Ca from the slow‐growing coral Siderastrea siderea, from the Dry Tortugas, Florida, has been generated that documents that robust proxy climate records of the tropical Atlantic and IntraAmerican Seas can be produced from this massive coral. The time series contain a 20‐year‐long calibration window (1973–1992) for both δ18O and Sr/Ca and a 73‐year‐long verification window (1900–1972) for Sr/Ca. These time series permit the quantification of the relationship between coral δ18O‐SST and Sr/Ca‐SST and the assessment of the stability of the proxy relationships over time. Both coral geochemical records are highly correlated with the augmented instrumental SST record through the calibration period, and Sr/Ca remains highly correlated through the verification period both at the bimonthly (r = −0.97) and annual average resolution (r = −0.72). Coral δ18O and Sr/Ca are highly reproducible within the same core, and Sr/Ca exhibits no extension‐related vital effects. This study sets the stage for generating multicentury scale climate records from the tropical Atlantic Ocean using the skeletal geochemistry of this massive, but slow growing coral.