HR: 1330h
AN: PP22A-1198    [PDF]
TI: Hydrologic Variability During the Last 10,000 Years in the Tropical Andes
AU: * Seltzer, G
EM: goseltze@syr.edu
AF: Dept. Earth Sciences, 204 Heroy Geology Lab Syracuse University, Syracuse, NY 13244 United States
AU: Rodbell, D
AF: Dept. Geology, Union College, Schnectady, NY 12308 United States
AU: Burns, S
AF: Dept. Geoscience, University of Massachusetts, Amherst, MA 0.003 United States
AU: Edwards, R
AF: Dept. Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455 United States
AU: Chen, H
AF: Dept. Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455 United States
AB: The apparent increase in frequency of strong El Ni\~{n}o events in the mid Holocene as recorded around the tropical Pacific (e.g., Moy et al., 2002, Nature) has prompted the search for additional records to help identify the mechanism(s) behind tropical climatic variability on interannual and longer time scales. Lake Junin is a large lake (300 km2) in the Peruvian Andes ($11\deg$S, 4100 masl) that has rapidly accumulated authigenic carbonate over the last 10,000 years. A 14C and U/Th dated time series of $\delta$18Ocalcite with an average sample spacing of $\sim$30 years shows up to $\pm$2$\permil$ (VPDB) deviations from an overall decreasing trend. The $\delta$18O of source precipitation to the region, as recorded in the Nevado Huascaran ($9\deg$S) and Nevado Sajama ($18\deg$S) ice-cores, reveals no decadal-centennial changes over the same time period and a long-term Holocene trend of $<$3$\permil$ (VSMOW). It is likely that large changes in the hydrologic balance (precipitation minus evaporation) of Lake Junin led to relatively rapid and large changes in $\delta$18Ocalcite . The hydrologic changes at Lake Junin can be correlated with El Ni\~{n}o events recorded in lake sediments in southern Ecuador, lake level records from Lake Titicaca, and the amount of ice-rafted debris in North Atlantic sediments. The variability in precipitation in the tropical Andes is likely a result of the interplay between air masses that deliver moisture to the Andes from the east and the upper tropospheric westerlies that are impacted by sea-surface temperatures in the eastern tropical Pacific(Vuille et al., 2000, JGR). Climatic conditions are generally drier in the tropical Andes during intervals marked by an increased frequency in El Ni\~{n}o Southern Oscillation warm events and cooler North Atlantic sea-surface temperatures.
DE: 1620 Climate dynamics (3309)
DE: 1655 Water cycles (1836)
DE: 1833 Hydroclimatology
DE: 4215 Climate and interannual variability (3309)
DE: 9360 South America
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting