A 156-YEAR TREE-RING OXYGEN ISOTOPE RECORD OF MAJOR HURRICANE EVENTS IN THE SOUTHEASTERN U.S

Temporally and geographically incomplete records hamper our ability to discern long-term trends and fluctuations in hurricane activity. Tree-rings provide a high-resolution and precisely dated record of hurricane activity that potentially extends many hundreds of years. The oxygen isotope composition of a-cellulose in tree-rings of slash and long-leaf pines serves as a hurricane proxy. Hurricane precipitation falls predominantly during latewood growth of southeastern pines (August to October). Hurricane precipitation is ¹⁸O depleted relative to normal seasonal rainfall and hurricane events are distinguished by relatively depleted latewood (LW) a-cellulose values and large differences in the d¹⁸O values of earlywood (EW) and LW for a given annual ring set (i.e., large, positive values of D¹⁸O EW-LW). We report a 156-year (1840-1996) tree-ring record of intra-annual EW-LW d¹⁸O values compiled from 2 specimens. Large intra-annual values of D¹⁸O(EW-LW) in a-cellulose correlate with modern meteorological and historical accounts of hurricane and tropical storm occurrence, particularly major hurricanes (class 3 or higher on the Saffir/Simpson scale). The decade of the 1950s and 1840-1880 showed particularly intense major hurricane activity, supported by historical records. The 1840-1880 time series of EW and LW d¹⁸O values show that this period is marked by relatively large D¹⁸O (EW-LW) values, even for non-event years, and, thus, hurricane activity may have been affected by larger than recent normal seasonal temperature differences or lower than average LW temperatures. Droughts can also be discerned in the tree-ring isotope and ring-width record and provide another important proxy record of climate. In some years, subsampling of LW rings permits better temporal resolution of the hurricane event by isolating the pulse of isotopically-light hurricane precipitation.