Arctic Shelf-Basin Interactions: Exchanges and Throughflows
Knut Aagaard
Polar Science Center, Applied Physics Laboratory University of Washington
1013 NE 40th Seattle, Washington 98105-6698, U.S.A
Tel: 1-206-543-8942
Fax: 1-206-543-3521
aagaard@apl.washington.edu
The focus in shelf-basin exchange studies has been on halocline and intermediate-depth ventilation, either by shelf waters made dense through brine rejection, or by Atlantic waters cooled during their transit of the Barents Sea. The dense waters likely enter the interior as plumes and/or trains of eddies, but we do not know the extent to which interactions with the slope boundary current are important. Where local processes drive the shelf-basin exchanges, these appear rather slow and strongly dependent on pre-conditioning of the shelf waters. Little regard has been paid to return flows. Salinity enhancement in coastal poynyas may be limited dynamically, but more diffuse sources of brine on the open shelf also appear important and are not thus limited. The most effective ventilation by shelf sources occurs when the cross-shelf circulation is part of a regional throughflow. There are two such sources: the input of the Atlantic across the Barents and that of the Pacific across the Bering/Chukchi. Recent measurements in Bering Strait show that on the average nearly 2,000 cubic km of water at the freezing point enter the Chukchi Sea each month during winter, with a monthly mean salinity as high as 34, but the interannual variability is large.
