Salt and Heat Budgets for the Gulf of St. Lawrence

Abstract

A simple box model expressing conservation of salt, heat, and mass for the top 50 m of four regions of the Gulf of St. Lawrence was developed. All available temperature and salinity data were combined with monthly estimates of freshwater input and surface heat flux to obtain an idea of the average annual variation in vertical and horizontal exchanges for the period March through December. Calculated horizontal transports agreed very well with available geostrophic calculations, and nutrient fluxes implied by the calculated upwelling of water from below 50 m are capable of supporting the estimated primary production in the Estuary and Northwestern Gulf. The main effect of the increasing freshwater discharge and surface heat flux in the spring seems to be a decrease in eddy exchange between the surface and deeper layers due to increased stratification.Key words: upwelling, horizontal transport, nutrient flux