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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 3, NUMBER 3, MARCH 1990

PROFESSIONAL PUBLICATIONS...
ATMOSPHERIC AND OCEANIC CHEMISTRY

Item #d90mar21

Nitrification Rates and 15N Abundances of N₂O and NO3- in the Western North Pacific," N. Yoshida (Dept. Earth Sci., Toyama Univ., Gofuku, Toyama 930, Japan), H. Morimoto et al., Nature, 342(6252), 895-897, Dec. 21/28, 1989.

Reports simultaneous measurements of the nitrification rates and isotope data. The amount of N₂O-produced nitrification is much lower than expected from the production of NO3-; N₂O in the oxygen-deficient layer is more enriched in 15N than NO3-. Results imply that the contribution of nitrification to the production of N₂O is lower than previously thought and that denitrification is primarily responsible for the production of N₂O.

Item #d90mar22

"Short-Term Changes in the Partial Pressure of CO₂ in Eastern Tropical Atlantic Surface Seawater and in Atmospheric CO₂ Mole Fraction," C. Oudot (Inst. Fr. Res. Sci. Develop. Coop. (ORSTOM), B.P. 1386, Dakar, Sénégal), C. Andrié, Tellus, 41B(5), 537-553, Nov. 1989.

Presents continuous CO₂ observations made at 3 long-duration oceanic stations (8 to 12 days) in the eastern tropical Atlantic. At the first location, the ocean surface was generally slightly undersaturated with respect to the atmosphere. At the second location, Guinea Dome, the ocean surface was an important source of CO₂ for the atmosphere. The net CO₂ flux calculated from mean data is lower (about 30%) than the net CO₂ flux calculated from data taken over short time intervals. In the Guinea Dome area in summer, the net CO₂ flux can be as high as in the equatorial area.

Item #d90mar23

"Modelling the Seasonal Contribution of a CO₂ Fertilization Effect of the Terrestrial Vegetation to the Amplitude Increase in Atmospheric CO₂ at Mauna Loa Observatory," G.H. Kohlmaier (Inst. Phys. Theor. Chem., Niederurseler Hang, Goethe-Univ. Frankfurt/M, D-6000 Frankfurt 50, FRG), E.-O. Siré et al., ibid., 487-510.

Previous global carbon cycle studies suggest that an observed increase of the amplitude of the seasonal cycle of CO₂ may be entirely due to a CO₂ fertilization effect on the terrestrial biota. Comparison of the modelled amplitude increase with the observed shows that external effects other than fertilization are operating. For instance: (1) the seasonality of the fossil fuel consumption in the Northern Hemisphere, which is nearly in phase with the relative uptake or release of CO₂ by the land vegetation, and (2) the seasonally different transequatorial transport of fossil fuel carbon.

Item #d90mar24

"Climate-Induced Feedbacks for the Global Cycles of Methane and Nitrous Oxide," M.A.K. Khalil (Inst. Atmos. Sci., Oregon Grad. Ctr., Beaverton OR 97006), R.A. Rasmussen, ibid., 554-559.

Measurements indicate CH₄ and nitrous oxide both decreased during the little ice age between 1450 and 1750; the authors believe these decreases were the response of emissions from the earth's soils, oceans and wetlands to global climatic change. The combination of the response of wetlands and permafrost to global warming may add as much or more CH₄ and nitrous oxide to the atmosphere as expected from increasing anthropogenic sources. The global warming that has apparently occurred over the past century may already have produced about 20% of the increase of nitrous oxide between the pre-industrial times and the present.

Item #d90mar25

"Seasonal Variation of Methane Emissions from a Temperate Swamp," J.O. Wilson (NASA Langley Res. Ctr., MS 483, Hampton VA 23665), P.M. Crill et al., Biogeochem., 8(1), 55-71, July 1989.

Methane flux measurements made at four sites over a 13-month period show a strong seasonal variation. Highest emission rates were observed in early spring and again in late summer in association with changes in plant growth and physiology. A comparison of flux measurements from fresh and saline wetlands in the immediate area of Newport News Swamp emphasizes the importance of edaphic factors in controlling flux.

Item #d90mar26

"Trace Gases in the Atmosphere Above the Ocean," V.M. Koropalov (Inst. Appl. Geophys.), YE.V. Kryukov et al., Izvestiya, Atmos., Ocean. Phys., 24(8), 1988 (translated edition Mar. 1989).

Presents measurements of several trace gases obtained during the Soviet-U.S. gas-aerosol experiments in the Pacific Ocean (SAGATEX-83). The zonal concentration gradients of CF2Cl2, CFCl3, CCl4, CH3CCl3, CH₄ and C2Cl4 in the ocean atmosphere are determined. Simultaneous measurements of the partial pressure of CO₂ in the surface layer of the ocean and in the atmospheric boundary layer are used to determine the flux of CO₂ between the atmosphere and ocean in the equatorial zone.