Xu, YuanyuanTropical sea surface temperature (SST) has been implicated as a driver of climate changes during the Medieval Climate Anomaly (MCA, 950-1300 CE) but little data exist from the tropical oceans for this time period. I collected multiple Diploria strigosa coral colonies from Anegada, British Virgin Islands (18.73°N, 63.33°W) in order to reconstruct climate in the northeastern Caribbean and tropical North Atlantic during the MCA. My Sr/Ca-temperature calibration results derived from three modern Diploria strigosa corals suggest that the temperature sensitivity for Diploria strigosa is -0.048 (±0.001) mmol/mol°C-1. My reconstruction of MCA climate suggests cooler and wetter conditions in the northeastern Caribbean during the late MCA, indicating that a Pacific La Niña-type climate pattern may have influenced local conditions. Additional analysis indicates that the North Atlantic Oscillation (NAO) was the principal driver of interannual climate variability during the late MCA.enThesisGeochemistry