Shelf-Break Upwelling Associated with Strong Upwelling Favorable Winds in the Chukchi Sea Suggests a Late-Summer Productive Zone Along the Shelf-Slope Boundary.
Abstract
Intensive oceanographic sampling in the Chukchi Sea in September 1996 revealed a dynamic northern shelf-slope boundary. In this year Chukchi Sea water was relatively warm and contained low nutrient concentrations, which differed considerably with the offshore water masses where a low-nutrient cold and fresher surface water resided above the nutrient rich cold and salty halocline waters. In early September, the Chukchi waters resided over the shelf areas and typical flows northward from the Bering Strait along the Alaskan coast (the Alaskan Coastal Current) forced shelf waters offshore or eastward along the Beaufort Sea. Late September differed considerably in that patches and plumes of cold, salty, nutrient-rich water was found on the shallow shelf in the region around Barrow Canyon and along the northern Chukchi Sea. Analysis of the winds occurring over the last 40 years showed that late summer-early fall is a period of transition from relatively light winds to 2-3 months of stronger upwelling favorable winds. During summer of 1996 winds were considerably stronger than the 40 year average, and upwelling favorable conditions were initiated in mid September after a period of downwelling in early August. The strength of the winds was sufficient to temporarily reverse direction of flow of the Alaska Coastal Current. Importantly, the upwelled waters from the cold nutrient-rich halocline were associated with strong subsurface chlorophyll maxima. Numerous references over the last three decades have reported halocline-like waters on the shelf in late summer or fall. This suggests that the seasonality in the regional wind field strongly influences water exchanges in the shelf-slope boundary region. Furthermore, if the events recorded in the literature mimic those seen in 1996, primary productivity could be significantly enhanced during these spatially and temporally frequent events in the region of the shelf-slope boundary. This could imply a much richer ecosystem and much faster organic matter cycling along the shelf edge than has been previously thought.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFMOS12A0268C
- Keywords:
-
- 4207 Arctic and Antarctic oceanography;
- 4219 Continental shelf processes;
- 4279 Upwelling and convergences;
- 4805 Biogeochemical cycles (1615);
- 4806 Carbon cycling