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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 3, MARCH 1999

JOURNAL ARTICLES...
OZONE DEPLETION

Item #d99mar21

“Arctic Ozone Loss Due to Denitrification,” A. E. Waibel et al.,Science 283 (5410), 2064-2069 (1999).

Total reactive nitrogen (all nitrogen oxides plus HNO3, ClONO2, and HO2NO2) was measured in the Arctic vortex in February 1995 and found to decrease by 50% between 16 and 22 km in altitude. This removal of active nitrogen from the gas phase by sedimentation into aerosol particles (here referred to as denitrification) is shown to substantially increase ozone loss in the Arctic stratosphere. Model results indicate that increased anthropogenic CO₂ will decrease Arctic stratospheric temperatures, enhancing denitrification and ozone depletion in the stratosphere over the Arctic. This effect will offset some of the gains made by banning CFCs in returning the polar stratospheric ozone levels to preindustrial levels.

Item #d99mar22

“Evidence for Bromine Monoxide in the Free Troposphere During the Arctic Polar Sunrise,” C. T. McElroy, C. A. McLinden, and J. C. McConnell,Nature 397, 338-341 (1999).

The vertical distribution of BrO, which is autocatalytically released from sea salt deposited on Arctic snow, was observed from high-altitude aircraft. Significant amounts of BrO were found in the planetary boundary layer and in the free troposphere. The BrO may have been transported there by convection over large openings in the ice pack. Ice crystals lifted upward by that convection provide reactive surfaces for reactions that affect the chemistry of the free troposphere and produce ozone loss.

Item #d99mar23

“UV-B Damage Amplified by Transposons in Maize,” V. Walbot,Nature 397, 398-399 (1999).

Increased UV-B exposure caused by stratospheric ozone depletion can directly and immediately damage plants by a variety of mechanisms. However, simulated field exposures of maize pollen to UV-B equivalent to a 33% ozone depletion also activated transposons that caused mutations and created phenotypic variegation (e.g., spotting). Whereas the cytotoxicity of a doubling of UV-B exposure would not affect agricultural output very much and whereas damage to DNA would be repaired or would result in stable mutations whose use could be avoided, the activation of cryptic transposons could increase the mutation rate in maize and other organisms, producing cycles of insertions and excisions long after activation