Plume dispersal in the Arctic Ocean - the Aurora Site at Gakkel Ridge

This thesis assesses the dispersal of the hydrothermal plume at the Aurora Vent Site in the Arctic Ocean, based on observational data and complemented by a numerical ocean model. The theoretical background of hydrothermal plumes in the Arctic is presented and the methods used are explained. This includes the processing of data acquired from a CTD probe, water samples and an oceanographic mooring with respect to the hydrographic setting and to the tracers for identification of the hydrothermal fluid. In addition a setup for simulating the plume dispersal with the Regional Ocean Modelling System is described. The observational results reveal a plume that ascends up to a height of 1200 m and spreads laterally to at least a distance of 2500 m, although a strong core is confined to a much smaller area. The plume dispersal is highly inhomogeneous for the different investigated tracers. This, as well as the small horizontal extent is explained by the presence of slow currents that are altered by tidal or inertial oscillations. A similar vertical extent can be obtained from the model simulation. However in regards to the currents and horizontal extent, the simulation shows large discrepancies compared to the observations, therefore suggestions for improving the model setup are presented.