Interpretation von FCKW-Datensätzen im Weddellmeer

Abstract

The aim of this thesis is to generate a circulation scheme of the deep water masses of the Weddell Sea with the primary objective to estimate production rates of different sources of these water masses using chlorofluorocarbon (CFC) data. Repeated observations of CFC for a section along the Prime Meridian from Antarctica (70°S) to approximately 50°S are presented for the period 1984 - 1998. In addition CFC data from the Weddell Sea section (Kapp Norvegia - Joinville Island) are considered. For various CFC features at this sections CFC time series have been generated, in particular for two deep cores of CFC-11 maxima adjoining the southern and northern margins of the Weddell Basin and elevated CFC concentrations over the Middle Atlantic Ridge. A new method of analyzing such CFC data has been developed. The outcome of this approach is the best fit of the age distribution, i.e. the fraction and the age of recently ventilated water. In contrast to previous methods more information about the age structure and a better error estimation could be derived. The convolution of the CFC and the velocity field results in the CFC transport through the section in this cores. The ratio of this value and the CFC surface concentration at the time of the water mass formation is an estimation of the transport of recently ventilated water within the core. Applying this to the deep cores at both sections a circulation scheme of the deep recently ventilated water could be estimated. From this scheme the production rates of the source in the western Weddell Sea and east of it (off Amery Ice Shelf) have been derived. Furthermore, the transport of the ventilated water of the mid-depth core has given an estimation of the productivity of the northern Weddell Sea. The comparison of these three sources has shown a surprising result: The production rates of all sources are in the same range (2.1±0.8 Sv western Weddell Sea; 2.4±0.8 Sv Amery Ice Shelf, about 3 Sv northern Weddell Sea).