Modelling the water exchange of a fjord system on the Swedish west coast

The water exchange between the Orust-Tjörn fjord system (located on the Swedish west coast) and the Skagerrak depends on different factors such as winds, tides, the water mass properties and circulation in the Skagerrak, as well as the density gradients between the southern and northern openings of the fjord system. These processes are not yet well understood as observations in the area are spatially and temporally sparse and the existing regional ocean models for the North Sea and Baltic Sea area have a too coarse resolution to sufficiently resolve the complex structures of the fjord system, such as the narrow and shallow channels that connect the different fjords in the system.

Therefore, we model the water exchange between the Orust-Tjörn fjord system and the Skagerrak using a NEMO3.6 model setup that has a horizontal resolution of 50 m. As validation, modelled temperature, salinity, velocity and sea surface height are compared with in-situ measurements. A detailed analysis of the modelled water flows in and out of the fjord system as well as between the different fjords will be presented. In addition, the different drivers of the modelled water exchange and their influence on the water properties above and below the sill depths in the fjords are investigated.