HR: 1340h
AN: PP43A-0596    [Abstracts]
TI: Chironomid $\delta$^{18}$O and $\delta$D as Paleoclimate Proxies: Progress and Puzzles
AU: * Axford, Y
EM: axford@colorado.edu
AF: INSTAAR and Dept. of Geological Sciences, Univ. of Colorado, 1560 30th St., Boulder, CO 80303 United States
AU: Miller, G H
EM: gmiller@colorado.edu
AF: INSTAAR and Dept. of Geological Sciences, Univ. of Colorado, 1560 30th St., Boulder, CO 80303 United States
AU: Wooller, M J
EM: ffmjw@uaf.edu
AF: Water and Environmental Research Center, Univ. of Alaska Fairbanks, 306 Tanana Drive, Duckering Room 437, Fairbanks, AK 99775 United States
AU: Francis, D
EM: dfrancis@geo.umass.edu
AF: Dept. of Geosciences, Univ. of Massachusetts Amherst, 233 Morrill Science Center, 611 North Pleasant Street, Amherst, MA 01003
AU: Geirsdottir, A
EM: age@hi.is
AF: Dept. of Geosciences, University of Iceland, Askja, Reykjavik, 101 Iceland
AU: Wang, Y
EM: ftyw@uaf.edu
AF: Water and Environmental Research Center, Univ. of Alaska Fairbanks, 306 Tanana Drive, Duckering Room 437, Fairbanks, AK 99775 United States
AU: Sauer, P E
EM: pesauer@indiana.edu
AF: Dept. of Geological Sciences, Indiana Univ., 1001 East 10th Street, Bloomington, IN 47405 United States
AB: An increasing number of paleolimnological studies are aimed at reconstructing lakewater isotopic composition, and thus (in appropriate hydrologic settings) the isotopic composition of paleo-precipitation. Records of \delta$^{18}$O and $\delta$D of paleo-precipitation are used to infer changes in climate, including changes in site temperature and storm tracks. This study investigates the viability of using the \delta$^{18}$O and $\delta$D of subfossil chironomid head capsules preserved in lake sediments to reconstruct lakewater isotopic composition. Chironomids (Chironomidae, or non-biting midges) spend much of their life cycle as aquatic larvae, and their chitinous larval head capsules are well preserved in many lake sediments. Wooller et al. (2004) demonstrated that chironomid \delta$^{18}$O and precipitation \delta$^{18}$O are strongly correlated along a transect from Greenland to Vermont (n=4, r$^{2}$=0.96). The goal of the current research is to further investigate the relationships between mean annual temperature (MAT) and the stable isotopic composition (\delta$^{18}$O and $\delta$D) of chironomids, lakewater, and precipitation. We have analyzed more than 100 samples from lakes in Iceland and Arctic Canada, including surface sediments from a transect of lakes representing a broad modern climatic gradient. Results confirm a correlation between chironomid \delta$^{18}$O and both lakewater \delta$^{18}$O and MAT. Chironomid $\delta$D also correlates with lakewater $\delta$D and MAT. On the other hand, preliminary results suggest differences in isotopic fractionation between taxa. Ongoing experiments are aimed at evaluating taxonomic differences and refining our methodology.
DE: 9315 Arctic region
DE: 3344 Paleoclimatology
DE: 1845 Limnology
DE: 1040 Isotopic composition/chemistry
DE: 1600 GLOBAL CHANGE (New category)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting