August. The other interpretation would be representative of mid-August when the flow 

 of warmer water around the west tip of St. Lawrence Island and westward from the 

 north side of Norton Sound leaves an isolated cold spot to the north of the east tip 

 of St. Lawrence Island. This situation is shown in the analysis by Hidaka 8 and the 

 late-summer data of University of Washington, 5,6 and can be seen occurring at the 

 80-foot level in our data. Further observations in this region are required to determine 

 the details of the development. 



The Intermediate Water separates the Alaskan Coastal Water and the Modified 

 Shelf Water. The Intermediate Water appears to originate in the region of Nunivak 

 Island and Cape Romanzof where the water is almost homogeneous from top to bottom. 

 The mechanism which brings about the pronounced uniformity is not definitely known 

 at the present. To the north of this region the Intermediate Water is maintained as a 

 transitional zone between the Alaskan Coastal Water and the Modified Shelf Water. 

 It nevertheless exhibits boundaries in the vertical profile with the other water masses. 



A schematic presentation of the water masses along a section from Wales south- 

 westward through the Strait of Anadyr, and the vertical distributions and the T-S 

 relationship at several stations along the section are shown in figure 9 (foldout). The 

 separation of the shaded water-mass types in the schematic diagram represents the 

 boundary between the water masses. In most cases this change is abrupt, but in some 

 cases the change takes place over a fairly broad region of transition as indicated by the 

 wider separation. 



The Alaskan Coastal Water is confined to a narrow region very near the coast. 

 The Modified Shelf Water lies along the bottom over most of the section and appears 

 at the surface in the center of the section near the Siberian Coast. At the surface, a 

 moderate sized area of Intermediate Water exists between the Alaskan Coastal Water 

 and the Modified Shelf Water, but at depths the Modified Shelf Water intrudes close 

 to the coast. Intermediate Water passing around the western end of St. Lawrence Island 

 is found near the surface near the southwestern end of the section. 



Deep Shelf Water is found on the bottom intruding from the southwest into the 

 Strait of Anadyr west of St. Lawrence Island. This water has approximately the same 

 salinity as the Modified Shelf Water but is colder and is separated from it by a marked 

 thermal boundary. The Deep Shelf Water is found also at stations 32 through 34 on 

 the south side of St. Lawrence Island. It is a persistent type and was found in this region 

 in both investigations conducted by the University of Washington (see NORTHLAND 

 station N-363, fig. 9). Both past and present data indicate that the Deep Shelf Water 

 intrudes from the southwest into the Strait of Anadyr, but during late summer does not 

 extend to the Bering Strait. Thus it appears that although there may be northward 

 movement of water along the bottom in this region, it is so slow that it is warmed 

 several degrees as it rises into the shoaler area north of St. Lawrence Island. In fact, 

 data from earlier sources indicate that this temperature boundary between Deep Shelf 

 Water and Modified Shelf Water recedes southward from the region of Bering Strait 

 as the summer season progresses. 



The whole system of water increases in density with distance from the Alaskan 

 Coast, except where the surface flow is interrupted by the barrier created by St. 

 Lawrence Island. From the density distribution and from the direct current observations 

 made in Bering Strait, 5,6 it appears that the water masses are flowing slowly north- 

 ward throughout the area, converging toward Bering Strait with a rapid flow being 

 concentrated near the coast in the Alaskan Coastal Water and at the boundary between 

 it and the Intermediate Water. 



12 



