#2.   What is the SST signature of a Scotian Shelf Cross-over?

Facilitator: Jim Bisagni
Rapporteur: Charlie Flagg

Jim Bisagni argued that cold temperatures aren't necessarily sufficient indicators of cross-over events, and it may be that the gradients around the edges of the intrusions are more robust. In order for gradients to be useful, they will need to extend back into the Channel and up onto Georges Bank. The use of gradients and their meaning may need to be linked to their location, timing, and duration, making them rather more subjective. Jim then revisited the 1992 SSC transport estimates (see Presentation E. above).

Peter Smith asked Jim B. what would be the most useful data that could be used to better define a cross-over plume, perhaps for future exploration? Jim replied that drifter data would probably be of most use. Charlie F. added that there might be an opportunity for dropping of air-deployed drifters when SST indicate the presence of a cross-over event. Jim also said that year-to-year differences in frontal probability maps could be used to indicate interannual variability in the number and intensity of the cross-over events. Diane Gifford noted that the broadscale cruise data are fairly dense when bongo hauls are included, so that these too would be useful in assessing the overall biological impact of the cross-overs.

Charlie F. suggested that the seasonal changes in stratification will impact the response of the Georges Bank waters to the cross-overs and the mixing that will occur with surrounding waters. Bob B. noted that the tidal flow in the Eastern Flank mooring location is very large -- bigger than that found along the southern flank. This would lead to vigorous mixing and a question arises about how the cross-over plumes maintain their integrity, if they do, as they transit that area. Charlie F. added that there is also vigorous internal wave activity on the NE Peak which dumps a lot of energy between the shelf break and the well mixed area which adds to the mixing energy that would tend to erode the cross-over plumes.