VARIABILITY OF CIRCULATION AND SEA ICE OVER THE EASTERN CANADIAN SHELF AND IN THE ADJACENT NORTHERN NORTH ATLANTIC OCEAN

Abstract

A significant gap remains in our understanding regarding the temporal-spatial variability of hydrodynamics over the eastern Canadian shelf (ECS) and in the adjacent northern North Atlantic Ocean (nNA). This thesis is a combination of studies on the dynamics of the large-scale circulation in the nNA and the processes affecting the circulation and sea-ice over the ECS. Based on output from a high-resolution model configuration for the years 1960-2009, the main physical processes driving the barotropic transport in the nNA were examined using a decomposition method based on the vertically-averaged momentum equations. This decomposition method has the advantage of revealing the major oceanic processes driving transport in the Gulf Stream and around the Labrador Sea and for diagnosing quasi-steady meso-scale features. Our results show that the potential energy term dominates the variability in most of the nNA in the model, while the mean flow advection and eddy momentum flux terms are important in the western boundary currents. A coupled ice-ocean circulation model is applied to the ECS and the adjacent northwest Atlantic to examine the impact of tides on the baroclinic circulation and temporal-spatial variability of hydrography and sea-ice over the ECS. The results show that the circulation and hydrography are affected significantly by tides in the Gulf of Maine, Bay of Fundy, Georges Bank (GeB), and the St. Lawrence River Estuary. Significant hydrographic anomalies are generated by tidal mixing and frontal circulations at tidal fronts, and then spread by residual circulations into broader areas. Strong internal tides are generated at the shelf edge southeast of GeB. The analysis of simulated sea-ice volume in the Gulf of St. Lawrence demonstrates a dominant balance between the open water ice formation and the basal melt at the ice-ocean interface. The former is significantly affected by the winter air temperature, while the latter is controlled by the stratification and circulation.