The Isotopic Records of Andean Ice Cores, a Response of Precipitation Variability Over the Amazon Basin
Edson
Ramirez, Univ. San Andres, ramglace@yahoo.com
(Presenting)
Three new ice-cores were drilled in the tropical and subtropical part of the Andes. The first one, 137 meters long, was extracted from the ice sheet of the Illimani (16º37'S, 67º46'W), a 6350m high mountain in the southern part of the Cordillera Real, Bolivia. The second one, 40 meters long, stems from the Sajama (6542 m, 18º06'S, 68º53'W), situated in the western part of the Bolivian Highlands. The third one, 56 meters long, was obtained at the summit of Chimborazo (6280 m, 1.6ºS, 78.6ºW) in Ecuador close to the ENSO influence region (Pacific Ocean). The isotopic composition of the ice as well as a number of various tracers (dust, calcium ions, electric conductivity) were analyzed in the laboratory and used for a year-by-year dating of the ice. A detailed comparison between the isotope signal of five different Andean high altitude sites (Huascarán, Quelccaya, Illimani, Sajama and Chimborazo) show a nearly identical inter-annual variability in the 20th century. An Andean Isotope Index (AII) constructed from these Andean sites has been compared with general circulation model simulations [Hoffmann et al., 2003]. The results suggest that the Andean high altitude records are primarily controlled by precipitation variability over the Amazon basin. The Illimani ice core record covers approximately the last 18 000 years BP and the analysis suggest that Illimani/Huascaran water isotope history can be explained in terms of a wetter/cooler conditions during glacial times to drier/warmer conditions in the Early Holocene [Ramirez et al., 2003].
References:
Hoffmann, G., E. Ramirez, J.D. Taupin, B. Francou, P. Ribstein, R. Delmas, H. Dürr, R. Gallaire, J. Simões, U. Schotterer, M. Stievenard, and M. Werner, Coherent isotope history of Andean ice cores over the last century, Geophysical Research Letters, 30 (4), 1179-1182, 2003.
Ramirez, E., G. Hoffmann, J.D. Taupin, B. Francou, P. Ribstein, N. Caillon, F.A. Ferron, A. Landais, J.R. Petit, B. Pouyaud, U. Schotterer, J.C. Simoes, and M. Stievenard, A new Andean deep ice core from the Illimani (6350 m), Bolivia, Earth and Planetary Science Letters, 212 (3-4), 337-350, 2003.