HR: 1340h
AN: PP43A-0603    [Abstracts]
TI: Reconstruction of the West Pacific ENSO precipitation anomaly using the compound-specific hydrogen isotopic record of marine lake sediments of Palau
AU: * Smittenberg, R H
EM: smitten@mit.edu
AF: Massachusetts Institute of Technology, Room E34 - 166 / 254 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Sachs, J P
EM: jsachs@mit.edu
AF: Massachusetts Institute of Technology, Room E34 - 166 / 254 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Dawson, M N
EM: mndawson@unsw.edu.au
AF: Coral Reef Research Foundation, P.O. Box 1765, Koror, PW 96940 Palau
AB: There is still much uncertainty whether the El Ni¤o Southern Oscillation (ENSO) will become stronger or more frequent in a warming global climate. A principal reason for this uncertainty stems from a glaring lack of paleoclimate data in the equatorial Pacific, which hampers model validation. To partly resolve this data deficiency, sediments of three marine anoxic lakes were cored in Palau, an island group that lies in the heart of the West Pacific Warm Pool. The lakes contain seawater that seeps through fissures in the surrounding karst, and they are permanently stratified due to fresh water input provided by the year-round wet climate (map 1970-2000 = 3.7m). During ENSO events, however, the islands suffer from drought. The surface water hydrogen isotopic compositions in the lakes are sensitive to the relative proportions of D-depleted rainwater and D-enriched seawater, and are therefore sensitive to ENSO events. The lake surface water H/D values are recorded by algal and bacterial biomarkers that are preserved well in the highly organic and anoxic sediments, which accumulate relatively fast (mean 1 mm/yr). Ongoing down core measurement will eventually result in a precipitation proxy record of the islands. To obtain endmember D/H values, a comprehensive set of water samples from sea, lakes and rain water was obtained, as well as suspended particulate matter. Higher plant biomarker D/H values derived from the jungle vegetation surrounding the lakes may render supporting climatic proxy data, being influenced by evapotranspiration. Some lakes are inhabited by millions of jellyfish (Mastigias) that live in symbiosis with zooxanthellae. The jellyfish of one of the investigated lakes disappeared completely after the last large ENSO event in 1998 (returning in 2000-01), and a correlation is suggested. To reconstruct the history of jellyfish occurrence, jellyfish and sedimentary lipids were extracted and compared. In addition to a possible ENSO proxy record, this information will contribute to a better understanding of the lake system and ecology of the jellyfish, providing a better basis for conservation efforts.
DE: 3344 Paleoclimatology
DE: 3354 Precipitation (1854)
DE: 4215 Climate and interannual variability (3309)
DE: 1040 Isotopic composition/chemistry
DE: 1055 Organic geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting