4. In\ estimation ot'the Physical Mechanisms Related toClimate 

 Variations 



Existing global physical models ot'the ocean-atmosphere 

 system do not make it possible to predict possible climate 

 changes on a regional scale because of the extreme complexity 

 of the modeled systems. Additional investigations of the 

 physical development of regional models, in particular of a 

 model for the Bering Sea. are an important need for long-term 

 climate forecasting at the present time. 



This problem could be solved on the basis of long-term 

 oceanological observations in different regions of the Bering 

 Sea. which are aimed at the acquisition of systematic information 

 on the vertical distribution of temperature, heat content of the 

 active layer and its variability with time, the structure and 

 variability of ocean circulation, heat transfer by the basic sea 

 currents, and heat and moisture fluxes across the sea surface. 



To develop the above models it is necessary to know the 

 regularity of water mass formation in the deep basins of the 

 Bering Sea. The following issues are not yet clear: North 

 Pacific water must be involved in bottom water formation, but 

 given the topographic isolation of Bowers and the central 

 basins, how and where docs this lake place? Are sources the 

 same for the different basins' What are the flushing rates (e.g.. 

 residence times)? 



There are three hypothetical mechanisms by which bottom 

 water might possibly be formed: /. modification of surface 

 (upper layer) water within the confines of the sea by cooling 

 and brine enhancement through ice formation, creating water 

 sufficiently dense to sink to the bottom: 2. subsurface mixings 

 of North Pacific water with appropriate Bering Sea waters as it 

 crosses the sills in the Aleutian-Komandorskiy Island arc 

 passages; and 3. direct advection of deep North Pacific water 

 in through Kamchatka Strait and then sequentially through the 

 gaps into the other basins. 



The BERPAC Program will investigate the mechanism of 

 deep water formation, renewal rates, and Hushing of the basins. 



Area of Investigations 



While selecting the study areas and location of stations in 

 the Bering Sea. the diversity and contrast of ecological conditions 

 in different regions of the sea were taken into account. 



In order to reflect a variety of ecological conditions in the 

 Bering Sea more completely, it seems appropriate that integrated 

 expeditions include work on polygons located in different 

 areas of the sea (with the purpose of obtaining representative 

 data on the structure and functions of the basic marine 

 ecosystems) and work across transects (with the purpose of 

 determining the space and time variations of the key ecological 

 parameters). 



Investigations within the framework of BERPAC will be 

 conducted on four polygons where investigations were carried 

 out in 1 98 1 (during the integrated ecological expedition aboard 

 the research vessel ( R/V ) Akademik Shirshov) and in 1 984 and 



1988 (during the second and third Soviet-American ecological 

 expeditions aboard the R/V Akademik Korolev) (Izrael & 

 Tsyban. 1987, 1990; Izrael etcd.. 1988a; Roscigno. 1990). 



Deep stations will be repeated at four centered polygons in 

 the four deep basins. The center station of each polygon will 

 also be a location for a mooring containing sediment traps and 

 current meters, funding permitting. Four other mooring 

 locations will cover the entrance from the North Pacific (in the 

 deep channel northwest of Komandorskiy Island), the main 

 gaps in the ridges north of Attu, and a location on the east side 

 of the Central Basin under the Bering Slope Current. The 

 mooring locations are also deep oceanographic stations, and 

 1 1 additional stations will provide continuity among the deep 

 waters. 



In addition to polygons, observations are planned at stations 

 along the transects located in areas that are not yet completely 

 understood, such as the Gulf of Anadyr, the Chirikov Basin, the 

 Gulf of Alaska, the northern portion of the Pacific Ocean, and 

 the deep-water central and southwestern areas of the sea. 

 Larger scale studies in the Chukchi Sea and central Pacific 

 ecosystems are also planned. The program for individual 

 expeditions will be discussed specifically during joint symposia. 



Proposed Observations 



Complex observations during the ecological expeditions 

 include meteorological (including aerological and geophysical 

 studies), oceanographical. and ecological observations. 

 Specifically, the following observations will be made: 



A. Meteorological observations will include routine 

 observations of meteorological parameters, such as studies of 

 direct solar radiation intensity and ultraviolet irradiation, cloud 

 and cloud type studies, and collection of samples of atmospheric 

 precipitation for chemical analyses. Aerological and 

 geophysical observations will include temperature and wind 

 sounding with the aid of radiosondes. Air samples will be 

 collected lor determination of sulfates and nitrogen oxides. 

 Visual observations of oil and oil product contamination on the 

 sea surface will be recorded. 



B. Oceanographic observations at designated sampling 

 depths in the water column will include temperature, salinity, 

 nutrients, oxygen content, water color and transparency, 

 biogenic elements, alkalinity, and petroleum hydrocarbons. 

 Tracers for water mass types will include stable isotope content 

 of seawater (oxygen, deuterium, tritium, freons, silica, and 

 carbon 14). In addition, current velocity and direction will be 

 determined, and sediment trap collections will be made. 



C. Ecological observations will include studies of the 

 atmosphere, sea surface microlayer, water column, and bottom 

 deposits in the environment. 



/. Atmosphere 



In rainfall. pH and the content of organic contaminants 

 will be determined. In dust particles, the content of organic 

 contaminants and metals will be determined. In the air at the 



