| Summary: | A polynya was observed three kilometres south of Hook Glacier in the northwest arm of Makinson Inlet in May 1973 . it was only possible to occupy four stations in the arm: Station I near the head, Station 2 in the basin just north of Hook Island, Station 3 about 200 m east of the polynya and Station 4 east of St. Laurent Point . The results from Station 2 showed that the water was almost isothermal at -1.80 °C, near the freezing point, with little salinity variation in the vertical column. The temperature at 125 m in Station 2 was nearly 0.5 °C lower than the temperature at the same depth in Station 4 in the waters of the main section of the inlet. . The resulting estimated volume of water in the inlet is 2.4 × 10**9 m³ which is considered accurate only to within a factor of three. . The estimated cross-sectional area, 1.5 × 10**4 m² is probably accurate to a factor of 2. . The mean value adopted for the volume of the tidal prism, 1.2 × 10**8 m³, is probably accurate to a factor of 2. The rate of loss of heat through the surface of the polynya can be estimated to be about 1000 langleys per day if the air temperature is taken as -30 °C, the water temperature as -1 °C and the mean wind velocity 5 m/sec. This gives a total heat loss during each flood tide over the 2 km² of the polynya of 5 × 10**12 calories. It is assumed that more or less complete mixing of the incoming tidal flow and the waters of the arm takes place on each flood tide. This assumption is justified, as a first approximation at least, by the state of homogeneity revealed by temperature and salinity observations. The resulting degree of cooling of the water in the arm would then be 3.0 × 10**-3 °C on each flood tide. If now it is assumed that the water in the arm had a similar temperature structure to that in the main inlet at the beginning of freeze-up, the difference between the average temperature in the deep basin and that in the main inlet in May must be due to additional cooling of the inflowing water as it ...
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