Simulation of wind-forced responses over the Newfoundland Shelf

摘要

A three-dimensional finite volume coast ocean model (FVCOM) is applied to understand better the wind forced oceanic responses over the Newfoundland Shelf including its embayments, especially during hurricane events. The hurricane-ocean model is applied over the Newfoundland Shelf to examine the mechanism that results in the significant coastal sea level rise and sea surface temperature drop. Model is coupled with Holland hurricane wind model to represent well the fast moving hurricanes. Hurricane induced coastal trapped waves are found through the analysis of tide-gauge sea level and currents. Turbulent mixing is the dominant process causing the sea surface temperature (SST) drop. The model is further applied to investigate the different oceanic response during Hurricane Igor (2010) and Hurricane Leslie (2012) on Placentia Bay. The model results agree reasonably well with field observations on sea level, near-surface currents and sea surface temperature (SST). The two hurricanes feature significant different tracks, radius and maximum sustainable wind, causing opposite shifts in inner bay circulation. The peak storm surge is significantly influenced by local atmospheric forcing during Leslie, but predominately due to remote forcing during Igor. Baroclinicity is important for the hurricane-induced inertial oscillation in the near-surface currents. The barotropic simulation results in a significant underestimate of the near-surface currents, including the inertial oscillation. FVCOM is finally applied off Eastern Newfoundland to study the circulation and hydrographic variability in 2000 and 2001. The model results along the eastern Newfoundland coast agree reasonably well with observations of sea level and currents. The model surface circulation patterns and temperature distributions in Trinity Bay in spring and summer reveal seasonal differences along the coast. Summer circulation shows significant upwelling along the western side of the bay, together with the emergence of two eddies in the bay. The generation of these eddies reveals the importance of nonlinear dynamics. The stratification along the Newfoundland coast shows the spatial differences and the seasonal and inter-annual change of stratification due to the wind stress and heat flux.