520 
fluctuations in the central region of the Strait, 
but for the period available (Fig. 19) a range 
of from about 5° to 1 1°C with an annual mean 
of 8.2 5 °C. is indicated. 
The temperature distribution with depth, as 
shown by bathythermograph records taken at 
shallow anchor stations, indicates a well-mixed 
region near the surface along Vancouver I. and 
Malcolm I. (Figs. 20-24). Except for slight 
anomalies the water is generally almost isother- 
mal, with temperatures during this period of ob- 
servation seldom above 11°C at the surface and 
falling to not less than 8°C at a depth of 20 m. 
As indicated from the anchor stations, there are 
no marked changes with time in this general 
picture of the vertical distribution of tempera- 
ture, and at any one depth the fluctuations in- 
dicated were less than 2 C° (Figs. 13-17). 
However, there is a slight difference (usually 
not more than 1 C.°) in temperature at the sur- 
PACIFIC SCIENCE, Vol. XV, October 1961 
face at most times of the year, with the water 
along the Vancouver I. side being warmer than 
that along the mainland side of the Strait. This 
is a result of the inflow of colder, less saline 
water from the mainland inlets. 
Seasonal data indicate that in general during 
the summer months the temperature at the sur- 
face is seldom above 10 °C. and at a depth of 
20 m. is seldom above 9°C. During the winter 
months it is seldom below 7.5 °C. at the surface 
but may be about 7°C. at a depth of 20 m. This 
picture of the vertical temperature distribution 
is somewhat modified during the winter as a 
result of surface cooling of the water down to 
a depth of about 20 m. and a temperature in- 
version has been observed in January which dis- 
appears by April. During this early period the 
water at the depth of 20 m. and, in places, even 
to a depth of 400 m., may be warmer than that 
in the upper 20 m. by as much as 1 C.° and 
MONTHS 
J FMAMJJ A S O N D 
Fig. 33. Monthly precipitation at Hardy Bay, B. C, for 1953. 
