HR: 0830h
AN: B11C-0712    [PDF]
TI: Tropical Cyclone Activity and Climate Fluctuations Captured by Oxygen Isotopes in Tree-Ring Cellulose From the Southeastern US
AU: * Miller, D L
EM: dmiller9@utk.edu
AF: University of Tennessee, Dept of Earth and Planetary Sciences 306 Earth and Planetary Sciences Bldg., Knoxville, TN 37996-1410 United States
AU: Mora, C I
EM: cmora@utk.edu
AF: University of Tennessee, Dept of Earth and Planetary Sciences 306 Earth and Planetary Sciences Bldg., Knoxville, TN 37996-1410 United States
AU: Grissino-Mayer, H D
EM: grissino@utk.edu
AF: University of Tennessee, Dept. of Geography 304 Burchfiel Bldg, Knoxville, TN 37996-0925 United States
AU: Mock, C J
EM: mockcj@sc.edu
AF: University of South Carolina, Dept of Geography 709 Bull St. Main Office Rm127, Columbia, SC 29208 United States
AU: Uhle, M E
EM: muhle@utk.edu
AF: University of Tennessee, Dept of Earth and Planetary Sciences 306 Earth and Planetary Sciences Bldg., Knoxville, TN 37996-1410 United States
AB: Tropical cyclone activity in the Atlantic Ocean and Gulf of Mexico fluctuates on seasonal to century scales. Large climate oscillations, such as the El Nino Southern Oscillation, Atlantic Multidecadal Oscillation, and the Pacific Decadal Oscillation may affect this tropical cyclone activity. To better discern and understand factors influencing long-term trends in hurricane occurrence, proxies are needed that extend the record beyond historical documents. Tree rings preserve excellent records of climate that can be tracked on an intra-annual scale. Two trees in southern Georgia, slash and longleaf pine, were collected and dated using dendrochronological techniques and a 156- year record (1840-1997) was examined. The tree rings were processed to alpha cellulose, with intra-annual resolution, for examination of oxygen isotopes from both earlywood (EW) and latewood (LW) growing seasons. In the southeastern U.S., temperature variation across the growing season for slash and longleaf pines is modest (27-33$\deg$C) and oxygen isotope compositions largely reflect the composition of precipitation. Tropical cyclones produce precipitation that is significantly depleted in $^{18}$O compared to average seasonal rainfall and generally occur during the LW growing season. The relatively depleted oxygen isotope ratios are incorporated into LW cellulose and thus the annual ring set is marked by a large difference between EW and LW $\delta$ $^{18}$O values. For years without a significant event, EW-LW differences are expected to be nominal. The 156-year long tree-ring oxygen isotope record of major hurricane occurrence corresponds well with known tropical cyclone occurrence in the study area. The record also captures evidence of EW drought. The tropical cyclone record appears to be overprinted upon a much larger climate oscillation that is characterized by periods of relative separation (i.e., apart from the larger differences due to hurricanes) vs. coincidence of the EW/LW oxygen isotope compositions. The frequency of tropical cyclones appears to be much greater during the EW/LW separation phase of this larger climate oscillation, in particular the decades of 1840 to mid-1920's and mid-1940 to mid-1970's.
DE: 0315 Biosphere/atmosphere interactions
DE: 1055 Organic geochemistry
DE: 1620 Climate dynamics (3309)
DE: 3344 Paleoclimatology
SC: Biogeosciences [B]
MN: 2003 Fall Meeting