The halocline of the western Arctic Ocean has distinct physical and chemical signatures associated with Pacific Ocean waters modified on the Chukchi and Beaufort shelves (Jones and Anderson, 1986). Important comparisons can be made between these shelves because they differ so significantly in terms of their geomorphic characteristics and the advective inflows which dominate their water masses (Pacific Ocean water in the Chucki Sea and Mackenzie River water in the eastern Beaufort Sea). Both of these shelves are among the more abundantly sampled regions of the Arctic Ocean and provide a basis for historical analysis, model building and hindcasting, and comparison with the other Arctic shelves.
Presently, shelf nutrients and dissolved organic matter (DOM) that are not assimilated by animals and plants in the western Arctic are exported to the basin (Walsh et al.,1997). Reduced export and increased light availability on the shelves should lead to larger primary production, based on enhanced nutrient uptake and recycling of the DOM. Most of the primary and secondary production in the Arctic takes place over continental shelves, directly influencing water column and benthic faunal populations (Grebmeier et al., 1995). In addition, benthic fauna in certain large shelf regions of the Arctic, such as the Chukchi Sea, directly consume carbon fixed by microalgae and these benthic organisms sustain huge herds of several marine mammal species that are culturally and economically important to the endemic peoples of the Arctic. Thus, changes in primary productivity over Arctic shelves could impact marine mammal populations through modification of prey populations.
3. GOALS AND OBJECTIVES OF THE SBI PROGRAM
Major goals for SBI will include studies of: 1) the interaction of physical mechanism (including ice) on advective processes and shelf-basin exchange, including the timing of physical movement relative to biological rate processes, 2) the fate of fixed carbon as it is advected, consumed (by pelagic and benthic consumers), or transformed, and 3) the overall effects of global change on various taxa and trophic structure.
In order to examine the influence of Arctic shelf-basin interactions on and in response to global change, the SBI program will address four main objectives. First, it will focus on shelf/slope water mass modification and exchange processes and biogeochemical cycles (Figure 2). An array of shelf-basin interactions (including cross shelf transport of fresh water and ice, halocline renewal via brine drainage and cooling, on shelf upwelling) have been shown to be responsible for maintenance of the stratification and ice cover of the upper Arctic Ocean.
