|Influence of wind on the Dutch Wadden Sea's freshwater dynamics
Brils, F. (2021). Influence of wind on the Dutch Wadden Sea's freshwater dynamics. MSc Thesis. NIOZ Royal Netherlands Institute for Sea Research: Yerseke. 57 pp.
The Dutch Wadden Sea is an important ecological area consisting of multiple interconnected coastal lagoons. Fresh- and salt water transport in the Dutch Wadden Sea is an important topic for conservation of the area. Classically the system was considered to be dominated by tidal flows but recent research has showed that wind-induced transport plays a key role on the variability of volume transport, making the Dutch Wadden Sea an event-driven system. This study attempts to gain a deeper insight into the influence of wind on the distribution of salinity and fresh water in the Dutch Wadden Sea.The General Estuarine Transport Model (GETM) was used to simulate the hydrodynamics of the Dutch Wadden Sea in three dimensions for the years 2005-2015. This model has been shown previously to match closely with measurements. The results show that the response to wind is dominated by transport between the various basins of the Dutch Wadden Sea. The response to wind depends on the location and is influenced by several factors. Important factors are the bathymetry, the distance from the sluices and whether the location is in the southern part of the Western Dutch Wadden Sea or not.To gain insight into the three-dimensional salinity distribution rather than the depth-averaged distribution, the salinity along a channel, which connects a freshwater source to the adjacent North Sea, was investigated. This channel responds most strongly to winds blowing from the North Sea to the freshwater source (westerly winds), increasing the salinity in the channel. Stratification in the channel is mainly influenced by the tides, showing a higher stratification during ebb and a smaller stratification during flood. This is also known as strain induced periodic stratification (SIPS). There is evidence that suggests that wind influences the stratification in the channel, but it is hard to distinguish the effect from variability in seasonal freshwater discharge and from laterally induced stratifying effects.