• 14C Profiles in the Central Weddell Sea

      Schlosser, Peter; Kromer, Bernd; Bayer, Reinhold; Münnich, K. O. (Department of Geosciences, The University of Arizona, 1989-01-01)
      14C data from stations in the central Weddell Sea are presented and discussed using additional parameters (potential temperature, salinity and 3He). The low 14C concentrations of the surface water (approximately equal -90 per mil) are explained by suppressed gas exchange due to ice cover during the winter and rapid turnover of the surface layer caused by entrainment of Warm Deep Water (WDW) with low 14C concentrations. A simple time-dependent balance calculated for the Surface Water (SW) and the underlying Winter Water (WW) can reproduce the 14C concentrations observed in these layers for 1985. The pre-bomb 14C concentrations are estimated at approximately equal to -130 per mil for SW and -140 per mil for WW. A strong deviation of the SW 14C concentration observed in 1973 from the calculated value suggest a change in surface circulation and/or air/sea exchange during the period before the Weddell Polynya in 1974. The observed 14C concentrations of the Weddell Sea Bottom Water (WSBW; -135 to -150 per mil) are only slightly higher than those of the WDW showing that the uptake of bomb 14C in the Weddell Sea is limited. The 14C profiles show a minimum at intermediate depths (approximately equal to 1500m) which is caused by radioactive decay and/or penetration of bomb 14C from shallow and deep layers (WDW and WSBW) into intermediate layers.
    • Fast 14C Sample Preparation of Organic Material

      Dörr, Helmut; Kromer, Bernd; Münnich, Karl Otto (Department of Geosciences, The University of Arizona, 1989-01-01)
      A fast 14C sample preparation technique for organic material in conventional 14C counting is described. The basic difference from conventional preparation is oxidation of the organic substances in a closed system under an oxygen pressure of ca 10 bars. After the explosion-like combustion, the reaction products SO2 and NO2 are oxidized immediately to SO4^-2 and NO3^- and precipitated on the wall of the reaction vessel. The residual gis mixture is passed first through a cold trap at -78 degrees C to remove water vapor and then through an activated charcoal column at 0 degrees C for purification. CO2 is removed from the remaining O2-CO2 gas mixture in a LN2 trap at a pressure approximately equal to 100mbar. With this method sample preparation time is reduced from ca 10 hr to ca 1 hr. The efficiency and reproducibility of the procedure is shown with 14C and 13C measurements of a sugar-carbon standard. The results obtained by the new technique agree well with conventionally prepared wood and bone samples.
    • The Continental European Suess Effect

      Levin, Ingeborg; Schuchard, Joachim; Kromer, Bernd; Münnich, K. O. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Observations of 14C in atmospheric CO2 at four different sites in central Europe, Heidelberg, Westerland, Schauinsland and Jungfraujoch have enabled us to determine individual fossil-fuel contributions to atmospheric CO2 concentration. The data clearly show a decrease of fossil-fuel CO2 with distance from anthropogenic source regions. At Heidelberg during winter we observe 14C/12C ratios up to 10% lower than at the clean air mountain station Jungfraujoch in the Swiss Alps, corresponding to an anthropogenic CO2 contamination level of ca 10% at the Heidelberg site. The Schauinsland and Westerland winter fossil-fuel CO2 concentrations are only ca 1.5 and 2% of the mean concentration, respectively. Our results indicate a strong seasonality in the European fossil-fuel CO2 source with ca 50% lower CO2 emissions during summer if compared to winter fossil-fuel CO2 release. This effect may significantly contribute (by 1-2 ppm) to the observed annual cycle of atmospheric CO2 concentration in northern mid-latitudes.