HR: 1330h
AN: PP32B-0292    [PDF]
TI: Compound Specific D/H Analysis of Late Holocene Lacustrine Sediments in Sub-Tropical North America: Implications for Reconstructing Atmospheric Circulation Patterns and Hydrologic Conditions.
AU: Cross, E
EM: ECROSS@MARINE.USF.EDU
AF: UNIVERSITY OF SOUTH FLORIDA, COLLEGE OF MARINE SCIENCE, 140 7TH AVE S. , ST. PETERSBURG, FL 33701
AU: * Hollander, D
EM: DAVIDH@MARINE.USF.EDU
AF: UNIVERSITY OF SOUTH FLORIDA, COLLEGE OF MARINE SCIENCE, 140 7TH AVE S. , ST. PETERSBURG, FL 33701
AU: Huang, Y
EM: YONGSONG_HUANG@BROWN.EDU
AF: BROWN UNIVERSITY, GEOLOGICAL SCIENCES, 324 BROOK ST BOX 1846, PROVIDENCE, RI 02912
AU: Van Vleet, E
EM: VANVLEET@MARINE.USF.EDU
AF: UNIVERSITY OF SOUTH FLORIDA, COLLEGE OF MARINE SCIENCE, 140 7TH AVE S. , ST. PETERSBURG, FL 33701
AB: The hydrogen (D/H) isotopic composition of individual organic compounds has the potential to provide high-resolution reconstructions of paleoclimatic and hydrologic conditions (e.g. atmospheric circulation patterns, relative humidity, etc) in continental environments. Modern calibration studies have shown that specific fatty acids are unique to algae (C-16) and terrestrial (C-28) materials, and that $\delta$D(C16) is more depleted than $\delta$D(C28). In lacustrine systems, the $\delta$D(C16) is a direct reflection of the isotopic composition of the source water it was synthesized in which, is determined by atmospheric circulation patters that governs latitudinal sources and seasonal amounts of precipitation. The $\delta$D(C28), on the other hand, reflects an isotopic enrichment of source waters resulting from evaporative processes experienced by most terrestrial vegetation. The magnitude of isotopic offset between the algae and terrestrial markers, ($\Delta$$\delta$D(C16-C28) ), takes into consideration variations in the source waters and, hence, reflects only the relative intensity of evaporative processes or the conditions of relative humidity. Together, $\delta$D(C16) and $\Delta$$\delta$D(C16-C28) from lacustrine archives can serve as proxies for the reconstruction of climatic conditions in continental settings. Lake Tulane, located in Central Florida, is a subtropical, groundwater-fed acidic lake with a high sedimentation rate and well-preserved organic matter. Its small catchment area allows for synchronous deposition of terrestrial and algal materials into the sedimentary record. Variability in the $\delta$D(C16), reflecting source water changes, and variability in the $\Delta$$\delta$D(C16-C28) has been observed in a sedimentary record from Lake Tulane representing the last 80kyr. On glacial-interglacial time scales, sea level is the dominant control on regional relative humidity in Florida and the long-term record of $\Delta$$\delta$D(C16-C28). This study focuses on reconstructing higher resolution continental climate change on decadal to interannual time scales with emphasis on specific climatic events such as the Little Ice Age and Medieval Warm Period. Over this interval sea level is largely invariant and we can attribute changes in $\delta$D(C16) to changing atmospheric circulation patterns (source waters), and the variance in $\Delta$$\delta$D(C16-C28) to fluctuations in the P/E ratios (relative humidity). These parameters provide a new set of proxies that can reconstruct hydrologic and atmospheric conditions in the geologic past.
DE: 0400 Biogeosciences
DE: 1040 Isotopic composition/chemistry
DE: 1845 Limnology
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting