Geophysics

Deep Reactions

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Science  21 Mar 2003:
Vol. 299, Issue 5614, pp. 1815
DOI: 10.1126/science.299.5614.1815c

Contaminants in ice cores can offer valuable evidence of past environmental change if they are not affected by processes occurring in the ice itself during their long periods of residence. Sometimes, though, the ice record can become overprinted by in situ formation of material, such as when excess CO2 is formed by reaction between the carbonate and acids contained in the ice. A new twist to this simple idea is reported by Colussi and Hoffmann, who show that CO in ice from Greenland is made by the action of ultraviolet Cherenkov radiation on organic matter. Cherenkov radiation is produced in glacial ice by the interaction of muons with the ice. Because muons can retain the energy required to form Cherenkov radiation for hundreds of meters, they can photolytically decarbonylate trapped chromophoric organic matter over great depths and long time intervals. Rates of CO production were calculated that are in substantial agreement with CO measurements in ice cores from Greenland that are younger than about 350 years. Thus, cosmic rays could perhaps generate other chemical signals measured in ice cores. — HJS

Geophys. Res. Lett. 30, 1195 (2003).

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