Holocene Climate and Environmental History in the Northeastern Caribbean

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Analysis of materials preserved as sediments in freshwater lakes underlies much of the scientific understanding of climate and environmental history world-wide. This study of lake-sediment cores from the island of Hispaniola will significantly strengthen terrestrial records from the tropical Atlantic region. Hispaniola provides a unique laboratory for analyzing Holocene changes in tropical circulation patterns because its mountainous terrain and the WNW-ESE orientation of its mountain ranges combine to produce areas in which precipitation is dominated by different moisture sources (e.g., trade winds; ITCZ-related precipitation; fronts associated with polar outbreaks). The investigators will examine pollen, charcoal, diatoms, stable isotopes, and C/N ratios in lake sediment cores obtained in three previous field seasons. The cores, which span the last two to seven millennia, are from two contrasting areas of modern vegetation and climate: Las Lagunas, a mid-elevation site on the southwestern flank of the Dominican Republic's Cordillera Central, and Laguna Saladilla in the northwestern lowlands. The different precipitation controls in these areas will allow the development of proxy records of vegetation and hydrological changes that reflect the history of northward extent of ITCZ-related precipitation (Las Lagunas) and the history of polar outbreak related precipitation (Saladilla). In doing so the new records will shed light on potential mechanisms as well as patterns of past climate shifts/events in the circum-Caribbean, including droughts at ~2400 cal yr BP and ~1200 cal yr BP that may have had significant impacts on prehistoric cultures. The study will also increase understanding of prehistoric human impacts on Hispaniolan landscapes, and on Holocene vegetation and fire dynamics, and will provide new context for interpreting previous records from Hispaniola and elsewhere. The tropics are crucial to our understanding of global change, past and future. This research is designed to increase our understanding of the Holocene histories of two important aspects of neotropical climate: migration of mean boreal summer ITCZ latitude in the Atlantic, and tropical influence of polar outbreaks. Efforts to develop and interpret these records can provide insight on possible future shifts in tropical climate, and their extratropical consequences. This project will also have significance for habitat conservation, management, and restoration. The research undertaken in this project will provide educational opportunities for several graduate and undergraduate students. Research results and scientific knowledge of global change will be shared through a "Visiting Scientist" program that the PIs and students will develop in local schools in collaboration with the Tennessee Geographic Alliance.