Circulation in the coastal waters to the west of Scotland was investigated using a three-dimensional, primitive equation ocean model. The coastline of this region contains many areas of outstanding natural beauty and over 60 sites of special
scientific interest. This, combined with the fact that the area is heavily used for fish farming and shipping and has potential for hydrocarbon exploitation, makes a better understanding of the regional oceanography essential. Particular interest was devoted to the non-tidal circulation, its seasonal development and its interannual variability.
These features were investigated using a version of the Princeton Ocean Model with a spatial resolution of approximately 6 km, and forced with real meteorological data from 1997. Model predictions were compared with observational data (CTD sections and current meter records) collected during the same year. The model was initialised with observational data and was smoothly matched to climatological temperature and salinity data at its open boundaries. It was shown that the model correctly reproduces the development of thermal stratification throughout the heating season. Salinity was reproduced with less success, model results showed less variability than observations; explanations can be found in the different physical mechanisms which control its temporal and spatial evolution.
The model was also used to simulate the baroclinic circulation that develops around a saline intrusion of Atlantic water in the Sea of the Hebrides, causing bifurcation of the northward flow around the Outer Hebrides islands. This feature of the circulation has been previously shown by limited deployments of satellite-tracked drifters. The model reproduced the Scottish Coastal Current and the recirculation in the Sea of the Hebrides showing t he importance of the baroclinic component of the flow. Rates of transport were calculated and were in agreement with previous estimates obtained with the help of radioactive tracers.