noted during 17-18 October (stations 89-92) 

 probably was the result of moving to the area 

 west of Cape Lisburne, instead of a change in 

 the weather patterns. Sea surface temperature 

 (fig. 7) followed a similar pattern of variation : 

 nearly constant during the early part of the 

 cruise (stations 8-30), with some variation 

 resulting from varying proximity to the edge 

 of the ice pack, and decreasing for the remain- 

 der of the cruise (stations 30-87). 



An area of low sea surface temperature 

 (<0° C) near shore near Cape Lisburne (sta- 

 tions 7^87, fig. 7) was the result of strong 

 cooling by the overlying cold air mass 

 (<— 10° C). Ice was rapidly freezing on the 

 sea surface as these stations were occupied, in 

 response to steadily decreasing air tempera- 

 ture. 



Variations in the surface wind field during 

 the cruise period (fig. 32) included two periods 

 of relative calm (most observations <10 kts), 

 which occurred during the early and middle 

 portions (stations 8-30, 25 September-5 Octo- 

 ber, and stations 45-60, 9-11 October). These 

 were interspersed with two periods of strong 

 winds (up to 35 kts) from the NNE-ENE 

 octant (stations 30-45, 5-9 October, and sta- 

 tions 60-85, 11-16 October). Time variation of 

 sea surface temperature showed a tendency 

 toward higher temperatures or a period of 

 slow decrease corresponding with the two 

 windy periods, probably because of mixing of 

 warmer, more saline, subsurface water with 

 the surface layer. In addition, the surface 

 temperature of the air mass involved in the 

 first windy period was higher than that ob- 

 served preceding or following the periods. 



Variations in meteorological conditions and 

 their effect on the distributions of surface and 

 near-surface water properties were large 

 enough to render the observed distributions 

 asynoptic over the full period of the cruise. 

 Consequently, the contoured sections of the 

 physical and chemical properties of the water 

 must be viewed with their asynoptic character 

 in mind, and inferences of flow based on these 

 sections can be considered valid for only short 

 periods of the cruise. 



Water Masses 



The temperature and salinity values observed 

 in the Cape Lisburne-Icy Cape area during 



WEBSEC-70 did not correspond closely with 

 water mass properties defined by Saur et al. 

 (1954) and Aagaard (1964) (figs. 33, 34). As 

 might be expected, the WEBSEC-70 values 

 were closer to Aagaard's fall values than 

 Saur's summer values. The lack of agreement 

 between the observed values and previously 

 defined water masses is not surprising, in light 

 of the wide time-dependent variation of the 

 properties of the shallow water of the Chukchi 

 Sea and the inflow from the Bering Strait. 



The surface water sampled in the Cape 

 Lisbume-Icy Cape area (designated by dots in 

 fig. 35) appeared to be a cooler, more saline 

 variety of the "Alaskan coastal water" defined 

 by Aagaard (1964). Underlying the modified 

 Alaskan coastal water often was found water 

 with T-S characteristics corresponding with 

 those of the "warm subsurface water" defined 

 by Aagaard (1964). Occasionally the warm 

 subsurface water was found at the sea surface. 

 Many of the T-S points fell between the two 

 water masses defined by Aagaard, which 

 merely exemplifies the need to adjust the 

 boundaries of the definitions. 



Rather than inventing new water mass defi- 

 nitions or modifying existing ones to fit the 

 observed properties, it may be simpler to con- 

 sider the physical processes and water masses 

 at the periphery of the T-S distribution which 

 influence the properties of the main volume of 

 water entering the eastern Chukchi Sea (fig. 

 36). Merely to facilitate discussion, the inflow- 

 ing water mass will be called Eastern Chukchi 

 Sea Fall Influx (ECSFI). 



Alaskan coastal runoff, both as a component 

 of ECSFI and as an addition to it north of the 

 Bering Strait, tends to produce higher tem- 

 peratures and lower salinities in the surface 

 layer. The volume of runoff, and accordingly 

 its influence on water properties, varies season- 

 ally, and from year to year. Because freezing 

 conditions were prevalent during WEBSEC-70, 

 the effects of runoff on the water properties 

 observed in the Cape Lisburne-Icy Cape area 

 were greatly reduced, yielding cooler and more 

 saline water than normally found during the 

 summer and fall months. 



Melting of sea ice will produce a surface 

 layer of cooler (as low as —1.8° C) and less 

 saline (<30 ppt.) water. A layer of water 

 whose properties were modified in this manner 



