Chain Lake is a small (46 ha), shallow (6 m) lake in the interior of British Columbia. In 1994, a hypolimnetic withdrawal system was installed to reduce internal nutrient loading. Associated monitoring included the physics of the lake response to meteorological forcing. This site provides a unique opportunity to compare theory to field observations of thermocline displacements and internal seiching because the lake is rectangular with uniform depth, and the dimensions are small enough (1600 m x 300 m) that the isotherm responses can be easily observed on a diurnal time scale. A series of profiles along the length of the lake were made under conditions of 'along lake' wind stress. Theory predicts that the thermocline will tilt downward in the leeward direction with a slope equal to the inverse of the bulk Richardson number. The limited number of observed thermocline slopes compare well to theoretical values. A meteorological station located at one end of the lake collected a time series record of water temperature within the water column and wind forcing. Spectral analysis of the time series reveals both diurnal cycles and non-diurnal cycles in the temperature response. During the mid summer, thermistors near the surface displayed a strong 24 hour period indicative of diurnal heating and cooling. At mid depth, however, the dominant period of oscillation was observed to be 10 hours indicating internal seiching and not a diurnal effect. For the summer season estimates of the seiche period using both linear and two-layer approximations are compared to the observed spectral responses of the thermistor times series. The observations of seiche period fall between those provided by these two prediction methods.
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