GRIP Oxygen-18 of Atmospheric Oxygen

REFERENCES: 

Chappellaz, J.A., E.J. Brook, T. Blunier, and B. Malaizé. 1997. CH4 and
d18O of O2 records from Antarctic and Greenland ice: A clue for
stratigraphic disturbance in the bottom part of the Greenland Ice Core
Project and the Greenland Ice Sheet Project 2 ice cores. Journal of
Geophysical Research 102:26547-26557.

Leuenberger, M.C. 1997. Modeling of the signal transfer of seawater d18O to
the d18O of atmospheric oxygen using a diagnostic box model for the
terrestrial and marine biosphere. Journal of Geophysical Research 102:26841
26850.

Sowers, T., E.J. Brook, D. Etheridge, T. Blunier, A. Fuchs, M.C.
Leuenberger, J.A. Chappellaz, J.M. Barnola, M. Wahlen, B. Deck, and C.
Weyhenmeyer. 1997. An interlaboratory comparison of techniques for
extracting and analyzing trapped gases in ice cores. Journal of Geophysical
Research 102:26527-26538.

Fuchs, A., and M.C. Leuenberger. 1996. d18O of atmospheric oxygen measured
on the GRIP ice core document stratagraphic disturbances in the lowest 10%
of the core. Geophysical Research Letters 9:1049-1052.

DATA DESCRIPTION:

See also the file d18Ogas.dat, which shows similar data from the Bern
laboratory for comparison. The file contains two columns:  

Column 1: Depth (meters below the surface).
Column 2: d18O values (permil against modern air taken in Normandie, 
	  France, in 1995).

d18O measured on oxygen in the bubble air from ice cores is a proxy for
continental ice volume and is used to synchronize cores from Greenland and
Antarctica (Bender et al., 1985, Sowers et al., 1993). A record measured
on ice samples from the Central Greenland deep ice core GRIP, spanning the
Last Glacial Maximum and the Holocene, shows that d18O of atmospheric
oxygen is in good agreement with measurements on the Vostok, Byrd and
GISP2 ice cores (Bender et al., 1994, Sowers and Bender, 1995). The smooth
isotope record of atmospheric oxygen represents a steady ice sheet decay
within the time resolution of about 2000 to 3000 years for atmospheric
oxygen. 

The Emian records as shown here documents the potential of d18O
measurements for tracing stratigraphic disturbances. Measurements
performed on ice from the GRIP core older than 100 kyrs (about 2700 mbs)
do not correlate with the corresponding Vostok record and show transitions
too fast to be typical for ice sheet build-up or decay. Furthermore, the
expected time lag between d18Oatm and d18O of seawater or d18O of ice is
absent or has even turned into a lead. Climatic interpretation of the fast
d18Oice transitions is not consistent with our d18Oatm results. By
combining our d18Oatm record with the methane (CH4) record at the same
depth levels and by comparing them to their Antarctic counterpart from
Vostok, we constrain the possible age of the ice in the disturbed region.
The combination suggests that the layers with heavy d18Oice correspond
indeed to ice from the last Interglacial (stage 5e) whereas layers with
light d18Oice correspond to ice either from stage 5d or from the
penultimate glaciation, mechanically inserted into the ice from stage 5e. 

DATA:

Depth (m)	del18O
Midpoint	(per mil)

2781.35	0.68
2785.2	0.46
2786.85	0.35
2789.05	0.32
2792.35	-0.07
2798.4	-0.11
2799.5	0.11
2801.15	0.67
2803.9	0.25
2808.3	0.35
2809.95	-0.21
2811.6	0.02
2816	0.11
2819.85	0.31
2824.8	0.19
2828.65	0.51
2830.3	0.57
2834.15	0.52
2836.9	0.85
2838	0.21
2847.9	0.49
2848.45	-0.31
2853.4	-0.25
2854.5	0.4
2856.15	-0.47
2857.8	-0.59
2860	0.21
2863.3	0.12
2864.4	0.01
2871.55	-0.33
2874.85	0.04
2880.9	0.08
2901.25	0.64
2908.4	-0.28
2910.05	-0.32