HR: 1340h
AN: PP33C-1599    [Abstracts]
TI: O2/N2 ratios in occluded air of the Vostok ice core and the GISP2 ice core and their relations with local summer insolation.
AU: * Suwa, M
EM: msuwa@princeton.edu
AF: Department of Geosciences, Princeton University, Guyot Hall, Washington Rd., Princeton, NJ 08544 United States
AU: Bender, M
EM: bender@princeton.edu
AF: Department of Geosciences, Princeton University, Guyot Hall, Washington Rd., Princeton, NJ 08544 United States
AB: In this paper, we extend earlier studies of variations of O2/N2 in the Vostok and GISP2 ice cores. This property varies at Vostok with local summer insolation, and may allow dating of deep Antarctic ice cores by orbital tuning. We report about 250 new O2/N2 measurements, all of which are from depths deeper than 1500 m of the Vostok ice core. We find that O2 is about 5 -10 per mil more depleted with respect to N2 than data reported by Bender [2002]. There is also more variability in a new set of measurements and we suspect that these fractionations are caused by O2 loss during core storage. In this study, we analyze the O2/N2 record created by compiling published data and new analyses. Wavelet analysis of the O2/N2 record on the d18Oatm orbital tuning chronology [Petit et al., 1999] shows a strong precessional signal between 100 and 350 ka and a strong obliquity signal later than 170 ka. A synthetic curve, derived by adding local variations of precession and obliquity, resembles well local summer insolation throughout the core, as previously inferred with less data. We exploit this observed relationship between the O2/N2 concentration ratio in occluded air and local summer insolation to derive a new Vostok ice chronology, and discuss the climate proxy records in the context of this new dating. Our tentative chronology shows that interglacial maxima of the Vostok temperature closely coincide with summer time insolation maxima at 65oN. Finally, we find that a precessional signal of O2/N2 ratios of the GISP2 ice core closely follows that of local summer insolation as well.
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 4926 Glacial
DE: 4932 Ice cores (0724)
DE: 4946 Milankovitch theory
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005