Seasonal-mean hydrography and circulation in the Gulf of St. Lawrence and on the eastern Scotian and southern Newfoundland shelves

Abstract

The climatological seasonal-mean hydrography and circulation in the Gulf of St. Lawrence and on the eastern Scotian and southern Newfoundland shelves are studied by reconstructing high-resolution temperature, salinity, and density fields for four seasons and numerically computing the associated circulation fields. The current fields are obtained from a three-dimensional diagnostic model, forced by baroclinic pressure gradients, seasonal wind stresses, and additional barotropic inflows across the Strait of Belle Isle and southern Newfoundland shelf upstream boundaries. The hydrographic fields suggest strong gulf-shelf interconnections, including outflow of relatively fresh surface water from the gulf to the eastern Scotian shelf, penetration of slope water at depth onto the shelves and into the gulf, and flow into the gulf through the Strait of Belle Isle. The circulation is generally cyclonic in the gulf, reinforced by inflows of Labrador and Newfoundland shelf water through the Strait of Belle Isle and Cabot Strait, while the circulation over the Scotian shelf is dominated by the southwestward shelf-break flow of water from the gulf and the Newfoundland shelf, with weaker flows from the gulf onto the inner and midshelf. Known major flow features such as the Gaspe Current, Cabot Strait outflow and inflow, and the Nova Scotian Current are realistically reproduced, and can be attributed to a combination of baroclinic pressure field and boundary inflow forcing. The model solutions are in approximate quantitative agreement with observed elevations, currents, and transports but with differences and notable uncertainties in some areas.