International Workshop on Exchange Processes Between the Arctic Shelves and Basins
Plenary Discussion Report
Day 1: Overviews, Role of Shelf and Slope Processes
P. Killworth and T. Weingartner
The day's talks had covered a variety of material, beginning with overview talks (Aagaard, Ikeda, Takizawa and Grebmeier) and then process-oriented talks mainly about exchange processes (Carmack, Melling, Muenchow, Pavlov, Schauer, Steele, Ohshima and Weingartner).
The discussion after these talks fell into three broad categories: processes, the requirements for observations, and general issues.
Processes
All the processes discussed involved responses to forcing of some kind (whether external, such as surface forcing fields, or internal, e.g. ocean conditions far from the shelf), and yet this was felt to be frequently the least well measured part of the system.The role of topography was frequently emphasised. In particular, the effect of eddies was important, perhaps produced by the Neptune effect along ridges and continental slopes, as well as direct eddy shedding as a mechanism to remove material from shelves.Topography also had a controlling feature (in a manner far from understood in general), with hydraulic control, flow through sills and straits, and the effects of canyons and ridges being of immediate relevance. Dense slope flows in the form of plumes, possibly amplified by sediment, were rather better modelled now than even five years ago.
Mixing was the second generic process. Again, eddies and instabilities had a dominant role, with the efficiency of their mixing limited by mechanisms which are not understood. (For example, can eddies mix material many deformation radii across a wide continental shelf so that dense water formed on the landward side can leave the shelf in a plume - a process which we have essentially never observed?) The mixing role of tides is not understood or modelled. Coastal waves, winds, and river inflow also produce mixing-like effects.
Ice dynamics, specifically the bounding effects of ice ridging on shallow shelves, but more generally the ice rheology, continue to need study, with new rheologies appearing recently. Testing, however, needs adequate forcing fields (see above), and
