Tropical cyclone frequency inferred from intra-annual density fluctuations in longleaf pine in Florida, USA

ABSTRACT: We present a new method for identifying historic tropical cyclone activity utilizing frequencies of intra-annual density fluctuations in longleaf pine in western Florida. In addition, in this work we provide information about the causal factors that determine the formation of intra-annual density fluctuations (IADFs) in longleaf pine latewood. Specifically, we test the viability of using late latewood (L+) IADFs in longleaf pine as a proxy for historic tropical cyclone frequency and precipitation for the period 1950-2017. The stabilized frequency of L+ IADF occurrence is significantly (p < 0.01) associated with the Palmer drought severity index (PDSI) for the months June through October, indicating that high amounts of late growing-season moisture promote the formation of IADFs in latewood. We find the strongest relationships between PDSI and IADF occurrence during September and October, indicating the influence of tropical cyclone (TC)-sourced precipitation on IADF formation. High IADF stabilized frequencies (i.e. >0.50) nearly always (88%) coincide with a TC tracking into the study area, and we find a significant (p < 0.01) relationship between TC-sourced precipitation and the stabilized frequency of L+ IADFs. Via this relationship, reconstruction of historic tropical cyclone frequency and precipitation is probable, which would allow for increased understanding of historic tropical cyclone activity prior to the historic climate record.