Attention is also drawn to the fact that not all shelf-basin effects come from immediately adjacent shelves, but that a distinction should also be drawn between near-field and far-field effects. For example, CFC data from the Canada Basin suggest a major ventilation has occurred in the 1990s, but the shelf responsible for this event is located in the Barents Sea (cf. McLaughlin, et al., in preparation).
Most work on shelf-basin interaction has focused on shelf outflow. But, arctic shelves are a two-way street, and we must also consider the equally important issue of basin waters moving onto slope and shelf regions prior to their exit into the North Atlantic. This is especially the case for outflow through the Canadian Arctic Archipelago Past views on the archipelago throughflow have considered it to be simple channel flow through a network of narrow passages (cf. Waddell, 1985, for modeling approach). New data, however shows the Canadian Arctic Archipelago, itself, to be extremely large and complex arctic shelf, studded with islands, and characterized by interconnected sub-basins.
Water within the Canadian Arctic Archipelago is clearly drawn from below sill depths in the adjacent Canada Basin. The very wide passages and sub-basins with the Canadian Arctic Archipelago allow for development of deep, gyre-like circulations, and waters with isolation ages of 20 or more years are observed to pool within these sub-basins, offering a potential sink for the high-latitude sequestration of CO2 (McLaughlin and Carmack, in preparation). Most of the freshwater transport through the system appears to occur in narrow (〜10 km) and shallow (〜20 m) buoyancy-boundary currents, flows that are usually overlooked in current measurement studies. The latter process in confounded by the fact that the distance between islands in Canadian Arctic Archipelago usually exceeds the local Rossby radius of deformation, so that processes maintaining the continuity of the flow becomes a question. Due to the irregular bathymetry and shoreline of the system, modified-tidal flow and resonance may locally dominate circulation
3. SUMMARY
Arctic shelves are critically important sites for water mass modification and primary production, and much work remains.
・ Cross-shelf exchange must distinguish critically between summer and winter conditions; re-current polynyas are likely key sites of brine production and submarine canyons are likely key conduits in shelf-basin exchange. Certain consequences of shelf-basin exchange may come from far-distant shelves, requiring a large-scale understanding of circulation in order to interpret local structures.
・ Of fundamental importance, the dynamics and forcing of the shelf-break current must be understood; is it wind, density, or topostrophically driven? What are the scales of motion?
. Circulation studies involving the Canadian Arctic Archipelago must thus consider selective withdrawal (in a rotating, stratified fluid), sub-basin gyre flows, buoyancy-boundary currents along irregular shorelines, and complex tidally-driven flows.
References
Aagaard, K., 1986. The Beaufort Undercurrent, in The Alaskan Beaufort Sea: Ecosystems and Environment, P. Bames and E. Reimnitz, eds., pp. 47-74, Academic, New York..
Carmack, E., and Ye. Kulikov, 1998: Low frequency currents, wind-forced upwelling. and internal Kelvin wave generation in the southeastern Beaufort Sea. J. Geophy. Res., in press.
Eby M. and G. Holloway, 1994: Sensitivity of a large-scale ocean model to parameterization of topographic stress, J. Phys. Oceanogr., 24,2577-2588.
Kulikov, Ye., E. C. Carmack, and R. W. Macdonald, 1998:Flow variability at the continental shelf break of the Mackenzie Shelf in the Beaufort Sea. J. Geophys. Res., in press.
