Open AccessO 2 /N 2 ratios of occluded air in the GISP2 ice core
Author(s) -
Suwa Makoto,
Bender Michael L.
Publication year - 2008
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2007jd009589
Subject(s) - ice core , geology , δ18o , isotopes of argon , paleoclimatology , groenlandia , dome (geology) , atmospheric sciences , physical geography , climatology , mineralogy , climate change , stable isotope ratio , ice sheet , geomorphology , physics , argon , oceanography , atomic physics , geography , quantum mechanics
We present and discuss the record of O 2 /N 2 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 δ O 2 /N 2 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 O 2 /N 2 ratio of samples is depleted by an average value of 7.3‰ during 11 years of storage at −35°C O 2 /N 2 ratios measured at various times were corrected for depletion during storage and combined to form a single data set. The stacked GISP2 δ O 2 /N 2 record shows strong spectral power at the orbital frequencies, and δ O 2 /N 2 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 δ O 2 /N 2 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 δ O 2 /N 2 , and by which temperature (or related properties) induce high frequency signals in δ O 2 /N 2 , remain to be identified.