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TEMPERATURE l°C) 



Figure G. — Observed water temperatures (°C) at selected depths in 

 Auke Bay, Alaska, 1960-68. 



the water column is isothermal to a depth of 50 m. In 

 April the surface waters begin to warm and start develop- 

 ment of a thermocline. Between April and July, surface 

 warming continues and by late July extends from 10 m. 

 A lesser gradient in temperature exists from 10 to 30 

 m, and below 30 m the temperature changes very little. 

 In the thermocline proper, a 10°C temperature dif- 

 ference may be encountered in July and August. After 

 mid-September, the thermocline decays because of 

 radiant heat losses and mixing by fall storms. The effect 

 of storms is to change the distribution of heat, as illus- 

 trated by the decrease in the temperature of the surface 

 waters to a depth of 10 m and a warming of the water 

 below 10 m by vertical mixing. Between October and 

 January, vertical mixing and cooling of the surface water 

 continue, and in January conditions are again isother- 

 mal to a depth of 50 m. 



Figure 7. — Typical profiles 

 of temperature (°C) in 

 Auke Bay, Alaska, for 

 January, April, July, and 

 October; data are averages 

 for 1960-68. 



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Salinity 



Figure 8. — Observed salinities ( °/ o0 ) at selected depths in Auke Bay, 

 Alaska, 1960-68. 



If we exclude those areas close to the outflow of large 

 rivers or close to melting ice, the salinities of the world's 

 oceans range from 32 to 38 %o . The salinities of es- 

 tuaries, however, are much more variable in time and 

 space, ranging from near zero to more than 30%o . This 

 wide variation is important as a selective agency in 

 determining the composition and structure of biological 

 communities. 



Variation of salinity at selected depths in Auke Bay 

 from 1960 to 1968 is shown in Figure 8. In general, the an- 

 nual cycle of salinity in the top 10 m was characterized 

 by 1) a period from January to April when salinity 

 remained between 29 and 31% > 2) a period between 

 May and July-August when salinity decreased to a 

 minimum of about 17%o, and 3) a recovery period 

 (September-December) when salinity increased again to 



