American Geophysical Union, Journal of Geophysical Research, G2(116), 2011
DOI: 10.1029/2009jg001194
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[1] Tree rings afford the temporal resolution needed to characterize extreme weather events such as tropical cyclones, their frequency and variability. External factors such as soil water isotopic variability, soil heterogeneity, and/or stand disturbance affect the isotopic composition of individual trees in a stand, resulting in inaccuracies in the record. Single-tree isotope chronologies should be tested against multiple-tree chronologies to determine whether individual trees sufficiently characterize tropical cyclone variability. Eight individual trees from two sites in Big Thicket National Preserve were analyzed to evaluate whether they synchronously record tropical cyclone events. The ability of individual isotope models to capture an event was low (<= 50%), and individual trees did not always record similar events. A composite chronology from the Turkey Creek Unit identified 5 false positive years and missed five storms. The composite chronology from the Big Sandy Creek Unit identified 5 false positives and missed four storms. All but 3 false positive years were characterized by above average precipitation that followed below average precipitation in the previous year. This mimics the negative isotopic excursion expected from tropical cyclones. Another year (1991) was coincident with a strong El Nino event, resulting in a shift in the dominant moisture source for the Texas Gulf Coast. Drought conditions occurred in years where storms were missed, which dampened the (18)O-depleted signal associated with tropical cyclones. These data show that the number of trees is critical for properly characterizing tropical cyclone frequency through time, especially for periods prior to reliable instrumental records.