Collaborative Research: Seasonal climate change over the last two millennia from archaeological sources in the subtropical eastern North Atlantic region

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How has the seasonal range in sea surface temperature (SST) changed over the last two millennia along subtropical coasts that are inherently sensitive to human and climate impacts? Seasonally-resolved records of preindustrial climate in subtropical coastal settings are few but critical to understanding impacts on humans and ecosystems. The goal of this research is to reconstruct summer and winter SST during four warm vs. cold climate intervals from the last two millennia. This will be achieved using paleoclimate proxies (indirect measures of SST) preserved in shells from archaeological deposits accumulated by aboriginal people in the Canary Islands. Outcomes will advance knowledge of human-climate interactions, such as the long-term effects of climate variability on prehistoric human subsistence patterns and behavior in ecologically sensitive habitats. This project will train students from high school to PhD level, targeting undergraduate students from low-income households, first-generation college students, and members of under-represented ethnic groups, using established programs including McNair Scholars, Women in Science and Engineering, and Upward Bound Programs. Through the UNC Baccalaureate Education in Science & Teaching program, future high-school earth science teachers will perform research that will generate laboratory curricula for K-12 science courses. This project fosters international and multidisciplinary collaboration among scientists from the US and Spain. Results will be disseminated to both specialists and the general public in both English and Spanish, which will engage a diverse audience in the US and elsewhere. Using oxygen isotope (delta18O) time-series of radiocarbon-dated archaeological Patella candei (Mollusca: Gastropoda) shells from the Canary Islands, several critical abrupt multi-centennial warming and cooling transitions (Roman Warm Period, Vandal Minimum or Dark Ages Cool Period, Medieval Climate Anomaly, and Little Ice Age) will be examined and compared to the late 20th century. The main goals are to: (1) calibrate and validate oxygen isotope sclerochronology (shell growth patterns) of living specimens of P. candei with instrument records as credible repositories of seasonal SST; and (2) reconstruct SST profiles from radiocarbon-dated archaeological shells during important abrupt climate intervals over the last two millennia relevant to our rapidly warming world. Results from this investigation will be then used to explore temporal variations of the North Atlantic Oscillation (NAO), which is a key feature of atmospheric variability in the North Atlantic and mainly operates during the winter. The geographic location offers a unique opportunity to examine the NAO phase and its shifts in the subtropical fronts during preindustrial warming and cooling climate episodes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.