Late Medieval Climate in the Caribbean: Pacific vs. Atlantic control on interannual variability and mean state

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The Medieval Climate Anomaly (MCA), an unusually warm period ~1000 years ago that was followed immediately by the Little Ice Age (LIA), represents a possible example of climate response to changes in radiative forcing. Previous work indicates that a change in the tropical Indo-Pacific sea surface temperature gradient may have contributed to the MCA; however, this change does not fully explain climate perturbations during that time, and the potential role of the Atlantic Ocean has yet to be considered. To fill this critical knowledge gap, a researcher at Chesapeake Biological Laboratory will generate a high-resolution paleoclimate record for the MCA and LIA transition using isotopes (Sr/Ca, δ18O) preserved in coral skeletons from the Caribbean Sea. The Caribbean is particularly well-suited for this study because Caribbean surface temperatures are strongly correlated with global surface temperatures; furthermore, while modeling has suggested a strong Pacific influence on Caribbean climate, this influence has not previously been tested with paleoclimate data. The paleoclimate record produced by this project will overlap temporally with pre-existing records from the tropical Pacific, enabling analysis of the relationship between the Pacific and Atlantic ocean basins with respect to short-term (centennial to inter-annual) climate variability. Understanding anomalous, short-term events like the MCA has important implications for assessing the limitations of long-term climate predictions. This project will advance knowledge of climate processes and variability in the heavily populated region of the Atlantic tropics. In addition, the project will support student training at the graduate and undergraduate levels, with undergraduate students provided by the Maryland SeaGrant REU program. A female, underrepresented minority student familiar with the study area (Anegada, British Virgin Islands) will participate as a student collaborator, and students at the University of Puerto Rico (a minority-serving institution) have been encouraged to join the field expedition. The field program will provide international experience for all students involved. Ongoing outreach programs at Chesapeake Biological Laboratory will incorporate this research.