HR: 0800h
AN: PP51A-0190    [Abstracts]
TI: Biogenic Tracers Through the Holocene on the Western Arctic Shelf
AU: * Lingle, C A
EM: carie.lingle@gmail.com
AF: Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529-0276, United States
AU: Gipson, B R
EM: bgips001@odu.edu
AF: Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529-0276, United States
AU: Cutter, L S
EM: lcutter@odu.edu
AF: Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529-0276, United States
AU: Cutter, G A
EM: gcutter@odu.edu
AF: Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529-0276, United States
AB: Present day changes in environmental conditions in the Arctic Ocean are causing substantial alterations in the ecosystem and as a result, fluxes of biogenic matter to the sediments. To place these recent changes in context, high resolution cores (multi- and piston-; up to 17 m in length) covering the Holocene and late Pleistocene were taken as part of the 2005 HOTRAX expedition on the Chukchi shelf north of Barrow, Alaska. These samples were analyzed for Org. C, N, S, biogenic Si, pyrite, mackinawite, and C,N isotopes. At Station JPC-5 (ca. 72.5° N, 157° W; 600 m water depth), highest organic carbon (2%) and nitrogen (0.2%) were found in the upper- most sediment and generally decreased with depth, with the lowest values (ca. 0.8% C and 0.1% N) in the early Holocene. The early Holocene also had very low S concentrations, consistent with low salinity, meltwater conditions. However, there were periods when elevated carbon fluxes occurred in the mid to late Holocene, some of which also had elevated biogenic silica concentrations presumably due to diatom blooms in surface waters. In this respect, atomic C/N ratios ranged from 9-13, consistent with inputs from algal organic matter (as opposed to terrestrial sources that were more prevalent in the early Holocene/late Pleistocene). We are currently making C and N isotope measurements to quantitatively evaluate these sources. These results compare well with cores from the Chukchi shelf taken in 1992 ca. 365 km to the northwest (200 m water depth), and suggest conditions were similar over an area much larger than that covered by just the HOTRAX coring. Processes controlling these biogenic fluxes will be discussed in terms of circulation and source proxies utilized by other HOTRAX participants.
DE: 4806 Carbon cycling (0428)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4924 Geochemical tracers
DE: 4999 General or miscellaneous
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting