HR: 11:05h
AN: PP22A-04    [Abstracts]
TI: Postglacial Climate Reconstruction Based on Compound-Specific D/H Ratios of Fatty Acids From Blood Pond, New England
AU: * Hou, J
EM: Juzhi_Hou@brown.edu
AF: Department of Geological Science, Brown University, 324 Brook St, Box 1846, Providence, RI 02912 United States
AU: Huang, Y
EM: Yongsong_Huang@brown.edu
AF: Department of Geological Science, Brown University, 324 Brook St, Box 1846, Providence, RI 02912 United States
AU: Shuman, B
EM: bshuman@umn.edu
AF: Department of Geography, University of Minnesota, 414 Social Sciences Building 267 - 19th Avenue South, Minneapolis, MN 55455 United States
AU: Oswald, W
EM: woswald@fas.harvard.edu
AF: Harvard Forest, Harvard University, 324 North Main Street, Petersham, MA 01366 United States
AU: Faison, E
EM: faison@fas.harvard.edu
AF: Harvard Forest, Harvard University, 324 North Main Street, Petersham, MA 01366 United States
AU: Foster, D
EM: drfoster@fas.harvard.edu
AF: Harvard Forest, Harvard University, 324 North Main Street, Petersham, MA 01366 United States
AB: Compounds of aquatic sources are of particular interest for compound-specific hydrogen isotope analysis because of their potential to record lake water D/H ratios which respond strongly to climatic changes (e.g.,temperature change). C₂₇,C₂₈ sterols and palmitic acid (C₁₆ n-acid) have been suggested to record D/H variation of lake and ocean water (Sauer et al., 2001, Huang et al., 2002, 2004). Here we report a new proxy of lake water isotope composition. Surface calibration from two transects indicates that behenic acid (C₂₂ n-acid) captures δD variation of lake water from two transects across eastern North America (δD_BA=0.8185*δD_water-140.01,R=0.898;p<0.05). We also determined hydrogen isotope ratios of individual fatty acids in a sediment core from Blood Pond, MA, in order to reconstruct climate change during the past 16 ka. Downcore variations in δD values of behenic acid and pollen taxa are highly consistent with known climate change histories in New England. Behenic acid is produced mainly by aquatic macrophytes. D/H fractionations of long chain even numbered fatty acids relative to lake water provide independent estimation of growth season relative humidity. Combined analyses of hydrogen isotopic ratios of short and long chain fatty acids from lake sediment cores thus allow reconstruction of both past temperature and effective moisture conditions. Comparison of δD records from two lakes in New England provides critical information on regional climate variation and abrupt climate change, such as 8.2 ka event. We also demonstrate that the chain length of fatty acids varies systematically in response to vegetation changes in the sediment core, providing additional data for paleoenvironmental assessment.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1637 Regional climate change
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4914 Continental climate records
DE: 4994 Instruments and techniques
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005