The Physical Oceanography of Bute Inlet, British Columbia

Abstract

Distributions of salinity, temperature, and oxygen of Bute Inlet based on twelve oceanographic surveys between the period August 1950 to July 1953 have been examined. The salinity structures of the shallow water during the various seasons can be classified under two main groups, one occurring at periods of small river runoff and the other at periods of large river runoff. In general, the surface salinity increases to seaward and with depth during all seasons. The surface water along the western shore is almost always observed to be less saline than along the eastern shore. The salinity of the deep water is 30.6 to 30.8% during both periods. The seasonal fluctuation of salinity at the surface is well marked, but below a depth of 60 feet no obvious cycle exists. The temperature distributions can be divided into two main groups, winter and summer. During both seasons the surface temperature generally increases to seaward. The temperature gradient in the upper layers during the winter is positive (increasing vertically downward) and during the summer is negative (decreasing vertically downward). From early spring to late autumn, a well-defined temperature minimum, in the middle and upper reaches of the inlet, is evident in the intermediate depths. The water in the greater depths has a temperature of 8.0 to 8.2[degree] C and remains almost unchanged throughout the seasons. A seasonal temperature variation is observed down to a depth of 150 feet and is in phase with the air temperature cycle, but be-low this it is less noticeable. Insolation and cold runoff water from the rivers are predominant factors in determining the fluctuation in the sea temperature. The concentration of dissolved oxygen is usually high in the surface layer. The water at the greater depth is not stagnant as evidenced by the oxygen concentration. Values from 0.2 to 1.5 g/cm/sec. for the eddy coefficient of conductivity have been determined for the intermediate depths.