The Currents in the Outer Oslofjord

This thesis is an investigation of currents in the outer Oslofjord using available tools. Current records and output from the NorKyst-800 model are examined and compared using statistical methods. Internal tidal waves are observed in the Drøbak Strait. Non-tidal frequencies are found to be the most energetic. The strongest currents are found near Bastøy, possibly associated with freshwater flow from Drammenselva. There are often two layers of current, of which the uppermost layer could be wind-driven and the second layer could be associated with the estuarine circulation. Topographic waves seem to exist near the bottom. Integral time scales are about one day. There is a weak clockwise turning of current with depth near the surface. In general, the current tends to go along-fjord. The currents are statistically Gaussian. Similarities to baroclinic modes with rough bottom are found. There are quite a few differences between the data and the model output, mostly due to the model bathymetry. Some differences, like the absence of bottom-strengthened currents, could be associated with a low vertical resolution. It is concluded that more current sensors recording over a longer time period, in addition to salinity and temperature loggers, are needed in order to fully understand the dynamics in the outer Oslofjord