Über die hydrographische Struktur der Deutschen Bucht im Hinblick auf die Verschmutzung in der Konvergenzzone

Abstract

It seems necessary to study the hydrographic structure of the German Bight (southern North Sea) in order to be able to understand the significance of the convergency zone for the pollution in this area. The hydrographic picture obtained is based on t° C, S ‰ and water current measurements. Dynamically, the convergency is a frontal zone in which two different bodies of water meet each other and are stratified. The water of the North Sea with its higher specific weight streams underneath the lighter coastal water. The horizontal and vertical distribution of density in this area creates irregular durations of high and low tides. Generally, low tides and their current run longer than high tides and their current. Data on the non-periodical rest current, based on distributions of S ‰ and density (σt), have been recorded; its speed is higher on the north Frisian than on the east Frisian side. The horizontal and vertical distributions of temperature and salinity in the German Bight cause strong t° C- and S ‰ gradients within the zone of convergence as well as pronounced seasonal differences. The convergency zone is important for the metabolic budget of this area, as it is likely that there exist close hydrographical, chemical, biological and geological interrelations. In springtime this area is oversaturated by oxygen due to intense plankton production. Moreover, it became evident that the convergency zone, with its high salinity gradient, forms an area in which several nutrient components like chalk, nitrate, phosphate, silicate (turbidity factor) accumulate. It was indeed possible to discriminate between different water bodies on the basis of the distributions of these nutrients. © 1968 Biologischen Anstalt Helgoland.