Coastal sources of estuarine inflow

Abstract

This dissertation considers the source of water that enters estuaries from the coastal ocean using a series of realistic and idealized ocean models. The first project examines the source of planktonic larvae of the marine invasive species, the European green crab (Carcinus maenas), which was observed in the eastern Salish Sea for the first time in 2016. Green crab spawns were simulated using particle tracking experiments in an ocean model of the eastern Pacific Ocean to investigate the likelihoods that larvae released from four potential source locations on the West Coast could be successfully transported into the eastern Salish Sea. The project determined that particle release timing and oceanographic processes (i.e. flow reversals in the Strait of Juan de Fuca) played a role in the probability of successful transport. The next project examined the sources of inflow to an estuary in an idealized three-dimensional primitive equation model with simple forcing. The model grid features an estuarine channel next to a sloping, unstratified shelf with mixing provided by a single frequency, 12-hour tide. Inflow is identified using Total Exchange Flow method (MacCready, 2011) in conjunction with particle tracking. When there are no shelf currents, the source of inflow is influenced by planetary rotation. In this instance, there may be important interactions between inflow and outflow. However, the third project demonstrates the response of estuarine inflow to the introduction of wind stress, also using idealized models. The rates and paths of estuarine inflow are found in five surface-forcing experiments: one control case without wind stress, two with downwelling-favorable wind stress, and two with upwelling-favorable wind stress. In these experiments, the source of inflow on the shelf is determined primarily by the direction of wind stress, and the impact of planetary rotation is much less significant. The last project considers the sources of inflow to the Strait of Juan de Fuca under two wind conditions. This was done using two particle tracking experiments and a realistic model of the Salish Sea and neighboring Pacific Ocean. In both experiments, inflow was sourced laterally from the up-wind direction. The Juan de Fuca canyon was a source of deep inflow in both experiments, suggesting submarine canyons may be an important conduit of inflow under all wind stress conditions. The results suggests that wind stress may be less important than other shelf dynamics on time scales longer two weeks.