A coupled circulation-ice modelling system with multi-grid nesting capacity was developed for the northwest Atlantic (CCIMS-nWA) based on the Regional Ocean Modeling System (ROMS) and Los Alamos Sea Ice Model (CICE). CCIMS-nwA is forced by atmospheric forcing (including winds, atmospheric pressure at the mean sea level and net heat and freshwater fluxes) at the surface, tidal forcing, inflows, hydrography and ice conditions specified at lateral open boundaries. The model external forcing also includes riverine freshwater discharges, and continental runoff due to melting of ice and snow over land. This paper provides an overview on different nested-grid setups developed by the regional modelling group at Dalhousie University for different projects. Performance of CCIMS-nwA is assessed using various data including in-situ oceanographic observations, satellite remote sensing data, and ocean reanalysis. Model results in two applications demonstrate the feasibility and skills of CCIMs-nwA in simulating both the large-scale hydrodynamics over the eastern Canadian shelf and fine-resolution currents and hydrography over three different coastal waters. These two different coastal waters include (a) southwestern Scotian Shelf, (b) Bras d’Or Lake of Cape Breton. The temporal and spatial variability of three-dimensional (3D) currents and hydrography simulated by this modelling system for these three coastal waters were examined based on time-dependent 3D model results.