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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 12, NUMBER 4, APRIL 1999

JOURNAL ARTICLES...
ICE CORES

Item #d99apr14

“Ice Core Records of Atmospheric CO₂ Around the Last Three Glacial Terminations,” H. Fischer et al., Science 283 (5408), 1712-1714 (1999).

Analysis of the air trapped in Antarctic ice cores was conducted at higher temporal resolutions than previously possible to determine the relationship between atmospheric CO₂ and glacial cycles. The observed relationship is complex, but in general, glaciation occurs before an increase in atmospheric CO₂ levels and remains high during some glaciations, which would seem to contradict global-warming theories that argue that increases in greenhouse gases will cause higher global temperatures. The key to the relationship is expected to be how the biosphere responds to the climate of the interglacial periods.

Item #d99apr15

“Holocene Carbon-Cycle Dynamics Based on CO₂ Trapped in Ice at Taylor Dome, Antarctica,” A. Indermühle et al., Nature 398, 121-126 (1999).

Analysis of more than 400 samples from an ice core taken at Taylor Dome in Antarctica showed that, during the early Holocene, atmospheric CO₂ concentration decreased slightly and then increased 25 ppmv between 8000 BP and the 18th century, adding 0.01 GtC to the atmosphere per year. The current rate is 3.0 GtC per year. The d13C fingerprint of the atmospheric carbon of the samples was studied and revealed that changes in the terrestrial carbon pool were the principal source of the increased atmospheric CO₂. Evidently, the vegetation absorbed CO₂ as it reestablished itself after the glacial period and then started leaking its sequestered carbon through decomposition.

Item #d99apr16

“Distortion of Isochronous Layers in Ice Revealed by Ground-Penetrating Radar,” D. G. Vaughan et al., Nature 398, 323-326 (1999).

Ground-penetrating radar was found to reflect buried layers of isochronously deposited snow, and such data from Fletcher Promontory, Antarctica, show arches and troughs in snow sheets up to 100 m deep. Many of these features result from the ice-surface slope and observed local anomalies in the vertical strain rate. The presence of these features requires that ice-core paleoclimatic records be corrected for such effects.