The main topics in Dietrich's 149 publications are: the dynamics of ocean currents, the stratification and mixing of water masses and their variability, the morphology of the ocean's bottom and the influence of topography on the spreading of water masses, and sound propagation in the ocean. During the work for his doctoral dissertation on the Agulhas Current System he was able to use data sets from the "Meteor" Expedition 1925-1927 and additional data from some other ships. For the first time the Agulhas Current System was described also in deep layers. He also compared the properties of the Agulhas Current and the Gulf Stream and described the Agulhas Current as a branch of the Atlantic circulation. He remained interested in the Gulf Stream, in particular in the relationship of pressure fields and currents and the origin of Gulf Stream water masses. With geography as an essential field in his education, he kept returning to morphological studies and to the relationship of topography and bottom water flow. He contributed considerably to the knowledge on the transport, distribution and mixing of water masses in the North Atlantic, the North Sea, the Baltic Sea and the Mediterranean. A selection of papers is cited here. The hydrographic atlas of the northern North Atlantic, produced on behalf of ICES, became an important collection of observational results. Following his work on semidiurnal and diurnal tides, he became a respected expert on tides in the open ocean. During a time when the tides in the open ocean had to be determined solely from coastal gauges, his tidal maps were considered a standard in the field. Dietrich was always prepared to use an holistic approach in marine research. He was interested in interdisciplinary problems, in particular the interactions between bottom topography and fisheries hydrography In his textbook he frequently discussed relations between the results of different disciplines.
