STUDY OF TEMPERATURE, SALINITY, AND CIRCULATION OVER COASTAL AND SHELF WATERS USING NESTED-GRID CIRCULATION MODELS

Abstract

The coastal and shelf waters (CSWs) support a wide range of human activities including tourism, recreation, transportation, and fisheries. Reliable knowledge of dynamics and temperature/salinity over the CSWs are of great importance to both human socio-economic concerns and the marine environment. In this thesis, three numerical modelling systems with different complexity are used to investigate the marine environmental conditions and important physical processes affecting their variability over the CSWs. Firstly, a Lagrangian particle tracking model is used to study retention and hydrodynamic connectivity of surface waters over the Scotian Shelf and its adjacent waters. The three-dimensional (3D) currents produced by the Princeton Ocean Model (POM) are used. The calculated near-surface retention is relatively low over western Cabot Strait, the inner Scotian Shelf, and the shelf break. The retention is relatively high in Northumberland Strait. Secondly, a four-level nested-grid coupled circulation-ice modelling system based on the Regional Ocean Modelling System (ROMS) and the Sea Ice Model (CICE) is used to investigate the 3D circulation and temperature/salinity in Halifax Harbour (HH), and landward intrusion of offshore sub-surface waters into Bedford Basin. Model results demonstrate that the persistent northwesterly winds are the most effective in triggering the intense landward intrusion than winds from other directions. Model results are also used in quantifying the cumulative effects of winds and tides on the time-mean currents and temperature/salinity in HH. Thirdly, a shelf circulation modelling system based on ROMS is used to examine the hydrodynamic responses of the northern South China Sea to Typhoon Linfa. Analysis of model results demonstrates the importance of storm-induced upwelling and vertical mixing in different stages of the typhoon, depending on the translational speeds, wind intensity and structure of the storm, and vertical stratification. Furthermore, the peak frequency of the storm-induced near-inertial oscillations (NIOs) is modified by the background large-scale circulation.