Fire Synchrony and the Influence of Pacific Climate Variability on Wildfires in the Florida Keys, United States

Abstract

We investigated relationships between climate variability and wildfires in endangered pine rockland communities in the Florida Keys, United States, using fire-scarred samples from the canopy dominant Pinus elliottii var. densa. To test broad-scale, spatiotemporal relationships between wildfires and climate, we compared cross-dated fire-scar chronologies from two islands in the lower Florida Keys, Big Pine Key (BPK) and No Name Key (NNK), to measured values of the Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO), El Niño-Southern Oscillation (ENSO; NIÑO3.4), Pacific Decadal Oscillation (PDO), Interdecadal Pacific Oscillation (IPO), and divisional temperature and precipitation over the period from 1856 to 1956. Large-scale climate anomalies captured by ENSO (NIÑO3.4) and IPO indexes had combined effects on widespread fires. Superposed epoch analysis revealed that widespread fires on BPK occurred during years that were drier than average and when constructive phases (years of combined warm [positive] or cool [negative] phases) of ENSO and the IPO occurred three years and one year prior to fires. Positive phases of the PDO were also significantly associated with widespread fires three years prior to events, but the PDO was not influential one year prior to fires. Although fire years were temporally synchronous between the two islands during the period between 1818 and 1924 (n = 10), we did not find significant relationships between climate and fire on the smaller NNK, which suggests that island size influences the ability to detect broad-scale climate forcing of wildfires in the Florida Keys.