Examination of circulation, flushing time and dispersion in Halifax Harbour of Nova Scotia

Abstract

This study examines the circulation, flushing time and hydrodynamic connectivity in Halifax Harbour based on three-dimensional currents produced by a multi-nested coastal ocean circulation modelling system. The time-mean currents produced by the modelling system feature two-layer estuarine circulation with a seaward flow in the upper layer and a landward flow in the lower layer in the Harbour. The hydrodynamics in the Harbour are also affected significantly by tides and wind forcing. Based on numerical passive tracer experiments, the estimated e-folding flushing time is about 40 and 90 days in the upper and the entire Bedford Basin, respectively. By comparison, the flushing time is about 2–5 days over the Inner and Outer Harbour, and only about 1 day in the Narrows. Analysis of passive particle trajectories carried by the model currents demonstrates that movements of particles in the Harbour are strongly affected by tidal and storm-induced currents. Hydrodynamic connectivity in the study region is also quantified in terms of a connectivity matrix calculated from particle trajectories.