Interannual variability of sea-ice cover in Hudson Bay, Baffin Bay and the Labrador Sea, and numerical simulation of ocean circulation and sea-ice cover in Hudson Bay.

In part 1, the spatial and temporal relationships between subarctic Canadian sea-ice cover and atmospheric forcing are investigated by analyzing sea-ice concentration, sea-level pressure, and surface air temperature, as well as ice thickness, runoff, and sea surface temperature, from 1953-1988. The sea-ice anomalies in Hudson Bay, Baffin Bay and the Labrador Sea are found to be related to the North Atlantic Oscillation (NAO) and the Southern Oscillation (SO). From the application of a spatial Student's t-test and a Monte Carlo simulation, we found that sea ice responds significantly to the SO event only in summer, and to the NAO event only in winter.A spectral analysis shows that sea-ice cover in Baffin Bay and the Labrador Sea responds to the SO and SAT fluctuations at about 1.7 year, 3-5 year and about 8-10 year periods. In addition, a sea-ice signature associated with the so-called "climate jump" during the early 1960s was found. The ice thickness and ice-melt date data are also used to verify the above findings.In part 2, the three-dimensional ocean general circulation model of Blumberg and Mellor (1983, 87) was used to simulate the winter and summer ocean circulation in Hudson Bay under specified atmospheric forcing and runoff. This model uses vertical sigma coordinates and horizontal orthogonal curvilinear coordinates. The vertical viscosity and diffusivity are computed using the Mellor-Yamada (1982) second-order (2.5) turbulence closure, while the values for similar horizontal parameters are calculated using the Smagorinsky (1963) parameterization. The new version of this model uses the semi-implicit scheme for the shallow water equations (Casulli, 1990). A consistent, modified radiation boundary condition has been developed for the surface elevation and the normal barotropic velocity for the universal multi-level, baroclinic model with strong vertical stratification. The surface cyclonic circulation in summer and winter, due in part to the boundary inflow from Roes Welcome Sound to the northwest of the domain, has been well simulated.In part 3, a dynamic thermodynamic model of sea ice with viscous-plastic rheology (Hibler, 1979; 1980) is used to simulate the seasonal cycle of sea-ice motion, thickness, compactness, and growth rate in Hudson Bay under monthly climatological atmospheric forcing. The simulated results for ice cover in other seasons also compare favourably with the observed climatology and with measurements from satellites. In particular, the model gives complete sea-ice cover in winter and ice-free conditions in late summer. (Abstract shortened by UMI.