HR: 11:05h
AN: PP42B-04    [Abstracts]
TI: Application of Foraminiferal Stable Isotopy to Quaternary Stratigraphy and Paleoceanography of the Central Arctic Ocean
AU: * Polyak, L
EM: polyak.1@osu.edu
AF: Byrd Polar Research Ctr., Ohio State University, Columbus, OH 43210, United States
AU: Adler, R
EM: adler.66@osu.edu
AF: Byrd Polar Research Ctr., Ohio State University, Columbus, OH 43210, United States
AU: Curry, W B
EM: wcurry@whoi.edu
AF: Woods Hole Oceanographic Instit., 266 Woods Hole Rd, Woods Hole, MA 02543, United States
AU: Ortiz, J
EM: jortiz@kent.edu
AF: Dept. of Geology, Kent State University, Kent, OH 44242, United States
AB: We synthesize new and published foraminiferal stable-isotopic (d¹⁸O and d¹³C) data from the Arctic Ocean's Northwind, Mendeleev, Alpha and Lomonosov ridges, including measurements from recently recovered HOTRAX'05 sediment cores. The majority of this data has been obtained on the >150 um tests of the dominant Arctic planktonic foraminifer, left-coiling Neogloboquadrina pachyderma. These adult specimens characterize subsurface waters, primarily the lower halocline that is ventilated by water mixing processes at the Eurasian Arctic shelves. Generally, stable-isotopic records from the central Arctic Ocean differ significantly from the typical oceanic stable-isotopic curves, especially with respect to d¹⁸O. Due to the relatively small size, nearly land- locked nature and the voluminous river input to the Arctic Ocean, d¹⁸O of foraminiferal calcite is controlled primarily by the composition of ambient water in which the principal end members are oceanic water and runoff during interglacials, or meltwater during glacial periods. As a result, Arctic stable-isotopic curves cannot be used directly as a chronostratigraphic tool; however, understanding their patterns is important for reconstructing paleoceanographic environments. Comparison of stable-isotopic records across the Arctic Ocean shows a consistent, dramatic change in their pattern. Whereas records from the Fram Strait and adjacent areas are similar to those from the North Atlantic by having temperature-controlled d¹⁸O variations, records from the Amerasia Basin have a very different pattern, with low d¹⁸O and d¹³C values characterizing glacial periods, and high values during interglacials/interstadials. Especially high d¹³C values occur in the interstadials such as OIS 3, while full interglacials such as OIS 5e seem to have intermediate values. We infer that glacial/deglacial stable-isotopic compositions are controlled by (1) high amounts of meltwater pooled in the Amerasia Basin and (2) a lack of halocline ventilation during low sea levels and glacial build-up on the Barents- Kara shelf. The opposite end member is represented by interstadials when water mixing was active on the Eurasian shelves, when freshwater fluxes were reduced due to the inundation of the Bering Strait and possibly reduced riverine discharge. Full interglacials are characterized by a somewhat intermediate regime, with considerable haline stratification and moderate subsurface ventilation.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 4926 Glacial
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting