PUMA
Istituto di Scienze Marine     
Longinelli A., Lenaz R., Ori C., Selmo E. Concentrations and delta C-13 values of atmospheric CO2 from oceanic atmosphere through time: polluted and non-polluted areas. In: Tellus Series B-Chemical and Physical Meteorology, vol. 57 (5) pp. 385 - 390. Blackwell Publishing, 2005.
 
 
Abstract
(English)
"CO2 is one of the primary agents of global climate changes. The increase of atmospheric CO2 concentration is essentially related to human-induced emissions and, particularly, to the burning of fossil fuel whose delta(13)C values are quite negative. Consequently, an increase of the CO2 concentration in the atmosphere Should be paralleled by a decrease of its delta(13)C. Continuous and/or spot measurements of CO2 concentrations were repeatedly carried out during the last decade and in the same period of the year along hemispheric courses from Italy to Antarctica on a vessel of the Italian National Research Program in Antarctica. During these expeditions, discrete air samples were also collected in 4-1 Pyrex flasks in order to carry out precise carbon isotope analyses on atmospheric CO2 from different areas, including theoretically 'clean' open ocean areas, with the main purpose of comparing these open ocean results with the results obtained by the National Oceanic and Atmospheric Administration/World Meteorological Organization (NOAA/WMO) at land-based stations. According to the data obtained for these two variables, a relatively large atmospheric pollution is apparent in the Mediterranean area where the CO2 concentration has reached the value of 384 ppmv while quite negative delta(13)C values have been measured only occasionally. In this area, southerly winds probably help to reduce the effect of atmospheric pollution even though, despite a large variability of CO2 concentrations. these values are consistently higher than those measured in open ocean areas by a few ppmv to about 10 ppmv. A marked, though non-continuous, pollution is apparent in the area of the Bab-el-Mandeb strait where delta(13)C values considerably more negative than in the Central and Southern Red Sea were measured. The concentration of atmospheric CO2 over the Central Indian Ocean increased from about 361 ppmv at the end of 1996 to about 373 ppmv at the end of 2003 (mean growth rate of about 1.7 ppmv yr(-1) in excellent agreement with the NOAA/WMO data from land-based stations). Simultaneously, the mean delta(13)C value of atmospheric CO2 over the Central Indian Ocean (Equator) decreased from -7.92 parts per thousand at the end of 1998 to -8.22 parts per thousand at the end of 2003; the mean decrease rate being of about -0.06 parts per thousand yr(-1). This rate as well as that calculated at 12 degrees S (-0.05 parts per thousand yr(-1)) are not far from the rates that may be calculated according to the data from the nearest NOAA sites (Crozet and Mahe islands); the rates calculated South of Australia and between Tasmania and N.Z. are almost identical to those calculated according to the data from Cape Grim NOAA site (Tasmania)."
DOI: 10.1111/j.1600-0889.2005.00166.x
Subject carbon-cycle
variability
sinks


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