Runoff 



The streams entering directly into Auke Bay are small 

 and drain low-elevation (less than 900 m) forested areas. 

 The streams are fed by rainfall and melting winter 

 snows, and discharge from them has several maxima and 

 minima each year that vary in timing from year to year. 

 These are Auke Creek, Auke Nu Creek, Wadleigh Creek, 

 and several smaller unnamed streams. 



The larger more distant Mendenhall River and Lemon 

 Creek discharge into Fritz Cove and Gastineau Channel 

 adjacent to Auke Bay. Their waters eventually enter 

 Auke Bay. The watersheds of these larger streams are 

 rocky slopes, ice and snow fields, and glaciers. The 

 monthly discharge follows an annual cycle, with a single 

 minimum in February or March and a single maximum 

 in July (U.S. Geological Survey 1964). The winter 

 minimum is caused by a decreased rate of snowmelt at 

 higher elevation and the summer maximum by a com- 

 bination of increased snowmelt and moderate precipita- 

 tion. 



Tides 



The tides in Auke Bay are semidiurnal and show diur- 

 nal inequality. The mean tidal range is slightly more 

 than 4 m (U.S. Coast and Geodetic Survey 1962). Spring 

 tides exceed this by almost 2 m. The times and heights of 

 high and low water are nearly the same over the entire 

 Auke Bay area. 



PHYSICAL AND CHEMICAL 



OCEANOGRAPHIC FEATURES 



OF AUKE BAY 



The Northwest and Alaska Fisheries Center Auke Bay 

 Laboratory has collected descriptive physical and 

 chemical oceanographic data in Auke Bay since 1959. 

 These oceanographic observations have been parts of a 

 variety of projects with differing needs and goals, so the 

 schedules and types of observations have varied over the 

 years. The seasonal cycles described in this report are 

 derived primarily from data collected from 1961 to 1967, 

 supplemented by some earlier and later observations. 



Five oceanographic stations (Fig. 2) were occupied 

 monthly during 1961-63. The local variations within the 

 bay were relatively small when compared with the fre- 

 quent transient vagaries. Oceanographic properties ap- 

 peared to be homogeneously distributed over the area of 

 the bay, and differences were usually within the limits of 

 error in our measurements. Consequently, beginning in 

 March 1963, the five stations were replaced with a single 

 midbay station. Auke Bay Monitor (ABM, Fig. 2) which 

 was monitored monthly for 1 yr. From March 1964 

 through July 1967, the ABM station was occupied ap- 

 proximately weekly in order to define more precisely 

 short-term variations in oceanographic conditions as- 

 sociated with use of amino acids as a nitrogen source by 

 the phytoplankton (Bruce 1969). 



The observations were made with conventional Nan- 

 sen bottles and reversing thermometers from the 

 research vessels Sablefish and Murre II and from various 

 small boats. The accuracy of the temperature 

 measurements was estimated ±0.05°C. Salinities during 

 the years 1959-64 were measured by titration, accurate to 

 ±0.01° /oo , and later by salinometer, accurate to 

 ±0.05%o. Concentration of dissolved oxygen was 

 measured by the conventional Winkler technique, ac- 

 curate to ±0.1 ml/liter. Phosphates, nitrates, and 

 silicates were determined by the methods of Strickland 

 and Parsons (1960) and are believed within the precision 

 limits of ±0.05, ±0.3, and ±3.0 ,ug-at./liter respectively. 



Temperature 



Water temperature is one of the most important 

 characteristics of marine environments. The dis- 

 tribution of water temperature and salinity influences 

 the physical mixing properties of the water. In addition, 

 temperatures, along with salinities, are useful in iden- 

 tifying masses of water and in monitoring changes in 

 physical and chemical properties of marine environ- 

 ments. Finally, temperature and temperature changes 

 affect metabolism and other processes in marine plants 

 and animals. Accordingly, this subject has been more 

 fully investigated than any other physical factor. 



The surface water temperature in Auke Bay ranged 

 from less than 2° to 17°C; an extended minimum oc- 

 curred between January and March and a maximum in 

 August (Fig. 5). Sea surface temperatures were greater 

 than the maximum air temperatures during the months 

 of November to February, reflecting large heat losses to 

 the atmosphere during the winter. Temperature 

 variations were greatest at the surface and decreased 

 with increasing depth (Fig. 6). At a depth of 50 m, the 

 temperature ranged from 2° to 7.8°C. The month of max- 

 imum water temperature was progressively later in the 

 summer at progressively greater depths. For example, 

 the surface maximum was reached in August, and the 

 maximum at 50 m was reached in October or November. 



During the year vertical temperature profiles change 

 from well mixed to strongly stratified (Fig. 7). In January 



" 



T 



1 1 i i i 1 1 1 i i 1 1 1 



Figure 5.— Monthly averages of daily maximum and minimum air 

 temperatures ( C C) recorded at Juneau, Alaska, airport and of sea 

 surface temperature (°C) at Auke Bay, Alaska, 1959-62. 



