Bibliography - M. Suwa
- Suwa, M., and Michael Bender, 2008: Chronology of the Vostok ice core constrained by O2/N2 ratios of occluded air, and its implication for the Vostok climate records. Quaternary Science Reviews, 27(11-12), doi:10.1016/j.quascirev.2008.02.017 1093-1106
[ Abstract ]We present a timescale for the Vostok ice core that is derived by orbitally tuning to O2/N2 ratios in
occluded air for depths deeper than 1550m (>112 ka), and by gas correlation to the GISP2 chronology
for the section shallower than 1422m (<102 ka). Our chronology of the deeper section rests on the
assumption that, during the bubble close off process, local summer insolation indirectly controls the
extent of O2 exclusion and hence the O2/N2 ratio in trapped gases. The newly derived O2/N2 chronology
is consistent with absolutely dated speleothem records. The O2/N2 chronology differs from previously
published orbital tuning chronologies (CH4 and δ18Oatm) by up to ~ ±6 kyr, and from the original GT4
chronology by up to ~15 kyr. The difference between the O2/N2 chronology and the δ18Oatm chronology
varies in time with strong signals centered at 1/100 and 1/41 kyr-1. The ages for the last four glacial
terminations in Vostok correspond to high obliquity (>23.7° at terminations’ midpoints). They also
correspond with decreasing precession index, corresponding to increasing boreal summer insolation.
The Vostok temperature record, boreal summer insolation, and the rate of change of the SPECMAP
property (reflecting planktonic foram δ18O) with respect to time are highly coherent at precession and
obliquity periods. These three properties vary almost synchronously, with the possibility that Vostok
temperature lags behind the other two. Our new timescale supports the widespread view that boreal
summer insolation played an important role in glacial–interglacial cycles.
- Suwa, M., and Michael Bender, 2008: O2/N2 ratios of occluded air in the GISP2 ice core. Journal of Geophysical Research – Atmosphere, 113(D1119), doi:10.1029/2007JD009589
[ Abstract ]We present and discuss the record of O2/N2 ratios in air occluded in the GISP2 ice
core retrieved from Summit, Greenland. In this study, we examine results for 601
samples from 331 depths measured by 1994, and 92 samples from 46 depths newly
measured in 2006. Poorly replicated samples, samples with no replicates and samples
falling more than three standard deviations from the mean of each δO2/N2 data set are
excluded from the analysis. The majority of poorly replicated samples are from the
depth zone associated with the transition between gas in bubbles and gas present as
clathrate hydrates. We found that the O2/N2 ratio of samples is depleted by an average
value of 7.3% during 11 years of storage at -35°C O2/N2 ratios measured at various
times were corrected for depletion during storage and combined to form a single data set.
The stacked GISP2 δO2/N2 record shows strong spectral power at the orbital
frequencies, and δO2/N2 is in antiphase with local summer insolation. This observation is
consistent with the earlier findings for the Vostok and Dome Fuji ice cores from East
Antarctica. It validates previous conclusions that fractionation during bubble close-off
depends on ice grain properties set at the surface by solar insolation. In addition, the
GISP2 δO2/N2 record shows millennial duration signals that are in phase with the local
temperature record of rapid climate change. The exact mechanisms by which local
summer insolation induces orbital variability in δO2/N2, and by which temperature (or
related properties) induce high frequency signals in δO2/N2, remain to be identified.
Direct link to page: http://cmi.princeton.edu/bibliography/results.php?author=3643
