HR: 1340h
AN: PP43A-0615    [Abstracts]
TI: Multi-proxy reconstructions of South American precipitation from oxygen isotopes and growth rings in tropical trees
AU: * Ballantyne, A P
EM: apb14@duke.edu
AF: Duke University, Box 90229, Durham, NC 27708-0229
AU: Baker, P
EM: pbaker@duke.edu
AF: Duke University, Box 90229, Durham, NC 27708-0229
AU: Chambers, J
EM: chambers@tulane.edu
AF: Tulane University, Dinwiddie 310, New Orleans, LA 70118-5698
AU: Villalba, R
EM: ricardo@lab.cricyt.edu.ar
AF: Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales, Box 330, Mendoza, CP(5500) Argentina
AB: Most of our knowledge about climate variability is restricted to the high latitudes of the Northern Hemisphere. Although the tropics constitute 40% of the Earth's surface, very little is known about temperature and precipitation variability, even during the last century. By analyzing the growth and isotopic variability of tropical trees, we may resolve intra-annual fluctuations in precipitation. Certain taxa of tropical trees are known to possess annual growth rings and some taxa exceed 1,000 years old. Recent progress in tropical dendrochronology, has established a strong relationship between growth and precipitation amount, especially during the growth season. The relationship between \delta$^{18}$O in precipitation and precipitation amount has been well established; and is moderately significant for certain regions of the neotropics (r= -65). Although much of the variability in the \delta$^{18}$O of precipitation has been ascribed to changes in sea surface temperatures resulting from El Ni¤o events, longer periods (12 yr.) of variability in \delta$^{18}$O remain unexplained. Here we combine measures of tree ring growth and \delta$^{18}$O in the cellulose of several tropical trees to capture the inter-annual variability in precipitation. Samples from the Andean genus Polylepis were cross-dated and analyzed for \delta$^{18}$O. The resulting 146-year time series reveals pronounced inter-annual variability in \delta$^{18}$O, as well as low frequency variability similar to the \delta$^{18}$O. An appreciable amount of regional precipitation is described by the ring-width and the high pass-filtered \delta$^{18}$O data. To validate the relationship between growth and cellulose \delta$^{18}$O, we also analyzed samples from Dipterix spp. and Tachigali spp. from the Amazon. In both taxa growth maxima and cellulose \delta$^{18}$O minima coincided during the rainy season (DJF). The analysis of \delta$^{13}$C, another isotope known to be fractionated under arid conditions may increase our ability to reconstruct precipitation over the last 500 years.
DE: 3344 Paleoclimatology
DE: 1615 Biogeochemical processes (4805)
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting