• 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.
    • Downward Movement of Soil Organic Matter and Its Influence on Trace-Element Transport (210Pb, 137Cs) in the Soil

      Dörr, Helmut; Münnich, K. O. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Data on depth distribution and 14C content of soil organic carbon, and on soil CO2 production in forest ecosystems are presented and discussed. Downward movement and turnover of soil organic matter is estimated from a box chain model. The downward transfer velocity of soil organic material depends on the litter material composition and on the annual rate of microbial decomposition. Depth distribution of 210Pb and 137Cs was measured. The identical transfer velocity of 210Pb and soil organic material suggests that lead transport is due to movement of the organic material itself. Lead in organic-rich soils obviously is bound rather tightly to the organic carrier by ion exchange or organic complexing. 137Cs migration depends on the turnover and downward movement of soil organic material. Results suggest that cesium is not transported only by the downward movement of solid organic matter, but, due to chemical exchange between the organic and hydrous phases, travels faster than organic matter.
    • 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.