Author(s): Y. E. Imam; B. Laval
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Abstract: ADCP velocity measurements in a small temperate lake are analyzed. From late summer to early winter, an ADCP was mounted on a sill (about 10.6m deep) separating two of three basins forming Pavilion Lake, British Columbia, Canada (maximum depth 62m). During the summer, along-thalweg velocity profiles show a regular response to the recurring daytime breeze that is channeled up-valley by the cliffs overlooking the lake. With the metalimnion engulfing the shallow sill crest, two-layer exchange of water between the two basins is directly forced by wind and reverses direction as the wind subsides each evening. Progressing into the autumn, the temperature stratification is eroded by convective cooling such that by late November the lake becomes isothermal and inversly stratifies afterwards. The wind regime also shifts to become dominated by synoptic-scale events partly channeled through the valley both in the same sense and opposite to the summer breeze. The along-thalweg water velocity profiles reveal an intensification in the exchange compared to the summer. The change in the flow pattern above the sill is thus a function of the seasonal stratification as well as the intensity and duration of the wind forcing. Description of this process in the lake comes as part of an effort to understand the physical setting for microbialite structures along the lake bottom but is also instructive for other small multiple-basin lakes subjected to similar wind regimes.
Year: 2009