Building a Cross-Dated Sea Surface Temperature Reconstruction for the Central Caribbean from Storm Deposit Corals

The Caribbean Sea is a primary moisture source for precipitation in the Americas and where warmer sea surface temperatures (SST) are driving increases in hurricane intensity and frequency. Furthermore, this sea has been identified as a "Hot-Spot" for sensitivity to global climatic change with direct social and economic ramifications for this region of 120 million people. Little Cayman Island is an ideal location for reconstructing past SST variations in the central Caribbean Sea and this island is frequently impacted by hurricanes that produce storm deposits consisting of numerous boulder-shaped corals. In 2016 and 2018, we collected 45 dead corals from the shoreline and lagoon of Little Cayman Island focusing on the coral species Siderastrea siderea, as well as a few Pseudodiploria strigosa and Orbicella faveolata; all species used in paleoclimatic reconstructions. Initial dating results reveals these corals span the last 800 years and with the largest corals containing 75 years of coral skeletal growth. Our primary goal is to develop a cross-dated coral-based SST reconstruction spanning the past 800 years for the central Caribbean using this collection of corals and our secondary goal is to examine age frequency of the storm deposits to better understand hurricane reoccurrence intervals for this island. The northern coast of this island has a NOAA Integrated Coral Observing Network station measuring hourly SST since 2009 thus allowing for direct calibration of the coral geochemical proxies. Historical records will be used to validate dates of storm deposits and tropical cyclones that impacted the island. Corals are subsampled for Sr/Ca analysis using a computer-aided micromill for precise sample extraction from the corallite synapticulothecal wall. Initial coral Sr/Ca results from S. siderea corals reveal seasonal Sr/Ca variations that track the NOAA station SST and Advanced Very High Resolution Radiometer SST with a calibration equation similar to that developed for this coral species in Gulf of Mexico and Haiti. Based on our work with S. siderea at several locations in the tropical Atlantic (Dry Tortugas, Flower Garden Banks, and Haiti), with boulder and microatoll colonies, we are confident this coral species will produce a stationary SST reconstruction spanning the past 800 years from storm deposit corals.