The water masses were oriented south to north across the 

 Chukchi Shelt'and were not exclusively related to bathymetry, 

 water from Bering Strait progressed northward through the 

 central Chukchi Sea and constituted a tongue of relatively high 

 surface salinity, with less saline water both on the west and east 

 sides (Fig. 2). 



Fig. 2. Surface honzontaldistnbutionsofsalinity( in parts per thousand: ppti 

 along the southern Chukchi Sea Continental Shelf. Alaska Coastal 

 water (<3 1 .5 ppl) lies to the east of mixed Bering Shelf- Anadyr water 

 031.5 ppt) which was situated immediately north of Bering Strait. 

 Siberian Coastal water (<3l..'i ppt) lies west of Bering Shelf- Anadyr 

 water between Kolyuchin Bay and Cape Dezhnev on the north coast 

 of the Chukchi Peninsula. 



Alaska Coastal water ( ACW) occurred in the eastern part 

 of the southern Chukchi continental shelf (Fig. 2). This water 

 mass is characterized by salinities <31.5 ppt, relatively high 

 surface temperatures (>6°C; Figs. 3,4), and a north-south 

 orientation along the coast of western Alaska. The transition 

 between this and the next water mass was weaker than between 

 the other two water masses (cf. Coachman el ciL. 1973). 



Mixed Bering Shelf-Anadyr water (BSAW; Grebmeier 

 et al.. 1989) was confined to the area immediately north of 

 Bering Strait between the two other water masses and is 

 characterized by salinities in excess of 31.8 ppt (Fig. 2), low 

 surface temperatures of -1 to -i-2°C, and a vertically mixed 

 water column (Figs. 3-6). The contribution of Bering Shelf 

 and Anadyr Waters to the southern Chukchi Shelf is especially 

 evident in Fig. 3, which illustrates a tongue of colder surface 

 water extending northward from Bering Strait into the Chukchi 

 Sea. Also, because isolines of temperature and salinity 

 (Figs. 4,5) were oriented more vertically along the southern 

 (e.g.. Stations 72-75) than along the northern, more stratified 

 sections, the separate identity and lack of lateral exchange of 

 water masses flowing north through the strait is apparent. 



60- (» 



Fig. 3. Surface horizontal distributions of temperature (in X) along the 

 southern Chukchi Sea Continental Shelf. 



To the east of BSAW and north of the Chukchi Peninsula, 

 Siberian Coastal water (SCW) occurred. This water mass was 

 characterized by very low surface salinities (24-31.5 ppt), 

 medium surface (3-5°C) and low bottom temperatures (-1 to 

 1 °C ), and a highly stratified water column ( Fig. 6). The bottom 

 salinity in SCW (Fig. 5, top) is also higher than that of water 

 from Bering Strait (Fig. 5, bottom). Siberian Coastal water is 

 thought to intrude eastward from the East Siberian Sea along 

 the Siberian coast (Coachman et al.. 1975). The tongue of 

 SCW during the 8-15 August 1988 cruise of the Akademik 

 Korolev (Fig. 2) extended further east than during the 24 July- 

 1 August 1972 cruise of the R/V Oshoro Maru 

 (Fig. 72, Coachman t7fl/., 1975). The transition between SCW 

 and BSAW was marked by very steep gradients of temperature 

 and salinity compared to the BSAW-ACW transition. 



Species Accounts 



Northern Fulmar (Fi</wfln<.;g/rtc/a//5) . Fulmar abundance 

 was highest (>2 birds km') in SCW (Tables 2,3). but this 

 procellariiform also occurred in BSAW and ACW in lesser 

 numbers. Colonies west of Provideniya on the Chukchi 

 Peninsula (D. Siegel-Causey & J. Piatt, personal 

 communication) and at St. Matthew Island in the central 

 northern Bering Sea (Sowls et al., 1978) would be the nearest 

 origins for fulmars in the Chukchi Sea. Both of these colonies 

 are south of Bering Strait (Fig. I ). 



Short-tailed Shearwater (Puffinus tenuirostris) . Short- 

 tailed shearwaters were >50 and >500 times more abundant in 

 SCW than BSAW and ACW, respectively (Table 2). This 

 austral species breeds in New Zealand, southern and eastern 

 Australia, Tasmania, and adjacent islands, migrating to the 

 Bering and Chukchi Seas during the Northern Hemisphere 

 summer (Hunt et al.. 1981 ). High concentrations have been 

 recorded at Aleutian Island passes (e.g., Unimak) during May- 

 June and September-October and northeast of St. Lawrence 

 Island during August-September (NOAA, 1988). 



383 



