Surface currents were measured with two 

 sizes of biplane drogues. The larger consisted 

 of two 60- by 60-cm. pieces of sheet metal 

 that were crossed on one another. Because 

 these drogues were supported in the upper 1 

 meter of water by a surface float, they are 

 called "1-m. drogues." The other drogues had 

 a similar design but were about a third as big 

 and are called "35-cm. drogues." We released 

 the 1-m. drogues in transects across the width 

 of the estuary and determined their subsequent 

 positions by approaching a drogue with a small 

 boat and visually estinnating its position. The 

 35-cm. drogues were used for special studies 

 and for observations close to shore. Wind and 

 tide conditions were recorded for each series 

 of releases. 



SEASONAL VARIATION OF 

 OCEANOGRAPHIC PROPERTIES 



Although the surveys were made indifferent 

 years, I assume that they indicate the major 

 oceanographic changes that occur seasonally 

 in any year. Therefore, I present the results 

 in a seasonal sequence regardless of the year 

 of sampling. The data are presented in a series 

 of figures (2- 12) as contoured vertical sections. 

 Outer Bay was sampled independently of tide 

 stage. Inner Bay was sampled at high tide and 

 at low tide, and the conditions at each stage 

 are presented separately. The dots on the 

 figures are the depths where measurements 

 were made. 



Temperature 



The water in Traitors Cove has a marked 

 seasonal thermal cycle- -it is nearly isothermal 

 vertically in winter, and a thermocline is 

 present in summer. In April the water in the 

 upper 30 m. in Outer and Inner Bays had only 

 small thermal gradients (fig. 2); the tempera- 

 ture at this time ranged from 6.0° to 7.4 °C. 



By June, increasing insolation had warmed 

 the surface water and formed a thermocline 

 in both basins of the estuary (fig. 3). Water 

 temperatures ranged from 9.6° to 13,5° C. 

 at the surface and from 7.5° to 8.8° C. at 

 30 m. 



Because of continued high insolation, water 

 temperatures in August in the estuary 

 were the highest observed (fig. 4). Maxima 

 were 16.9° C. at the surface and 11.9° C. at 

 30 m. 



On the October survey (fig. 5) the range of 

 surface water temperatures was reduced to 

 8.8° to 10.2° C. These lower temperatures, in 

 comparison with August, resulted from autumn 

 cooling (indicated by lower air temperatures 

 in October) and by vertical mixing (indicated 

 by higher water temperatures at 30 m. than in 

 August). 



The deep water of Outer Bay cooled through- 

 out the spring, summer, and fall. The tempera- 

 ture of the water at 75 m. in Outer Bay was 

 7.5° C. in April, 7.2° in June, 7.0° in August, 

 and about 6.5° in October. This cooling is 

 probably not a local feature, because the 

 temperature of the water at 75 m. in Behm 

 Canal followed a similar trend. 



Salinity 



The distributions of salinity in Traitors 

 Cove show the presence of a surface layer 

 with low salinity in summer and fall. This 

 layer is formed by the mixing of underlying 

 salt water with fresh water fronn runoff. 



In April (fig. 6) the salinity of the surface 

 water at the various stations ranged from 23.9 

 to 28.9 °/oo in Inner Bay and from 26.9 to 

 28.6 °/oo in Outer Bay. The salinity of the 

 deep water (greater than 30 m.)was greater 

 than 29.1 <yoo in both areas. 



Because of greater runoff in June, the 

 salinity stratification in both Outer and Inner 

 Bays was more intense than in April (fig. 7). 

 The salinity of the surface water at the sta- 

 tions in Inner Bay ranged from 5.4 to 17.0 "^00. 

 Outer Bay, with surface salinities in the range 

 19.1 to 24.3 °/oo, was less stratified than 

 Inner Bay. 



August 1963 was a month of unusually low 

 rainfall throughout southeastern Alaska. 

 (Ketchikan, for instance, received only 2.5 cm. 

 of precipitation- -about 9 percent of the long- 

 term mean for August.) As a result of the low 

 runoff, the salinity stratification in Inner Bay 

 was poorly developed (fig. 8). 



The salinity stratification of Outer Bay, 

 however, was not greatly affected by the low 

 local runoff. Large rivers in the region that 

 drain into Behm Canal and other passages 

 normally have peak discharges in July or 

 August due to snowmelt. These rivers pre- 

 sumably supplied the fresh water which entered 

 Outer Bay from Behm Canal and caused the 

 salinity stratification there. 



The net result of low local runoff and con- 

 tinued supply of low- salinity surface water 

 from Behm Canal was that the salinity strati- 

 fication in August was greater in Outer Bay 

 than in Inner Bay- -a reversal of the relation 

 observed at other times during this study. 



In October the local runoff was relatively 

 large, and salinity stratification was intense 

 (fig. 9). The salinity of the surface water ranged 

 from 0.0 to 18.8 °/oo in Inner Bay and from 

 24.0 to 27.1 °/oo in Outer Bay. The salinity of 

 the deep water (greater than 30 nn.) was at 

 least 30.0 °/oo in both bays. 



Dissolved Oxygen 



The concentration of dissolved oxygen was 

 relatively high (at least 5.0 ml./l.) in the 



