HR: 0800h
AN: PP51E-0645    [Abstracts]
TI: A High-Resolution Drought Record Spanning the Past ca. 800 Years From Sub-annually Laminated Lake Sediment, East Java
AU: * Crausbay, S D
EM: crausbay@wisc.edu
AF: Department of Botany, University of Wisconsin, 430 Lincoln Drive, Madison, WI 53706 United States
AU: Russell, J M
EM: russ0154@umn.edu
AF: Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912 United States
AU: Schnurrenberger, D W
EM: schno005@umn.edu
AF: DOSECC, P.O. Box 58857, Salt Lake City, UT 84108 United States
AB: A sub-annually laminated lake sediment core spanning nearly the last 800 years, from Ranu Lamongan, East Java, combines several characteristics that make it ideal for providing a potential record of ENSO variability. The sediment, which accumulated at rates in excess of 1 cm yr^-1, is well suited for high-resolution analysis. Composition of the dark and light couplets in the core suggest that these laminations form in response to seasonal changes in rainfall and water-column overturn in the lake, therefore providing well-defined seasonal resolution. A significant correlation between mineralogical changes (Mg/Ca) and δ ¹⁸O variations in authigenic carbonates suggest the basin is highly sensitive to hydrologic variation. Furthermore, lithologic data suggest authigenic carbonates precipitate and thus record hydrologic conditions during the dry season - a season in which rainfall anomalies in Indonesia are highly correlated with the phase of ENSO. Our carbonate-based record of Mg/Ca shows variability in evaporative concentration on a quasi-seasonal frequency for the past ca. 800 years. Our record shows two periods of drought - ca. 1275 to 1325 and ca. 1450 to 1650 CE - the latter of which was especially strong and/or prolonged. Our record also shows a possible change in drought frequency at around 1650 CE, in which periods of carbonate precipitation and Mg/Ca change shifted from multi-decadal to interannual variability. Given the strong correlations between modern-day drought in East Java and ENSO variability, our record may indicate a regime shift in the behavior of the ENSO system about 350 years ago. Finally, comparisons between our record and others suggest that paleoclimatic variation on centennial and sub-centennial scales is more strongly associated with changes in regional mean climate than with changes in the global mean climate state.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4922 El Nino (4522)
DE: 4942 Limnology (0458, 1845, 4239)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005