Exchange of water and oxygen between the two basins of Amisk Lake
1997
Lawrence, Gregory A. | Burke, J. M. | Murphy, T P | Prepas, E E
Amisk Lake was artificially oxygenated year-round by bubbling oxygen through a diffuser installed at the deepest point of its north basin. The hypolimnion of both basins became anoxic in summer before operation of the system whereas anoxia was never observed while it was fully operational (July 1990 until October 1993). The system increased the average hypolimnetic oxygen content of the south basin by an average of 83 tonnes (t) more than under natural conditions between 2 September and 18 May. This considerable increase is approximately accounted for by the transport of dissolved oxygen (DO) through the connecting channel by currents driven by the bubble plume (approx 52 t) and by internal seiche pumping (approx 17 t): both mechanisms are contingent on the thermocline depth being less than that of the connecting channel. Internal seiche pumping was possible because the connecting channel is shorter than the maximum distance across which hypolimnetic fluid moved between flow reversals. Other factors that may have been important include changes in the replenishment of DO during turnover, oxygen transfer during winter through the ice-free patch created by the bubble plume, and an increase in DO consumption.
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