EXPERIMENTS USING A LONG-TIME-SCALE SHELF CIRCULATION MODEL OF RELEVANCE TO THE LABRADOR CURRENT

Experiments are described using a three-dimensional, shelf circulation model. The model geometry consists of a rectangle in latitude-longitu de space with a shelf-slope region bordering the northern and western boundaries and a deep ocean region in the southeast. Relatively light water is flushed in through the northern boundary and allowed to exit through the southern boundary, a situation of relevance to the southwa rd flowing Labrador Current. In an earlier paper, we showed the downst ream development of a shelf break current. In that paper, bottom frict ion was parallel to bottom geostrophic velocity. In this paper, bottom friction is parallel to bottom velocity. This leads to a more diffuse downstream jet. We show that changing the density contrast across the front does not change its width. On the other hand, a sharper front i s obtained when a small trough is introduced into the bottom topograph y. We also describe an experiment in which the density of the inflowin g water is varied seasonally. This leads to a seasonal redistribution of the southward transport across the shelf, similar to a suggestion m ade by MYERS et al. [(1989) Seasonal and interannual variability of th e Labrador Current and West Greenland Current. Department of Fisheries and Oceans, Canada] for the Newfoundland Shelf. This redistribution r esults from the seasonal pulsing of fresh water down the shelf, which, in turn, influences transport through the Joint Effect of Baroclinici ty And Relief (JEBAR), and is similar to the mechanism proposed by LAZ IER and WRIGHT [(1993) Journal of Physical Oceanography, 23, 659-678]. Other results concern the splitting of the shelf break jet. We show t hat in the previous paper, the splitting of the jet was influenced by the numerical formulation of the outflow condition at the southern bou ndary. We also show that the splitting can be suppressed by specifying the density of water flowing into the model domain through the southe rn boundary, rather than allowing this to be determined by the previou s history of mixing and outflow on the boundary.