ABSTRACT: Seiches, circulation, and storm surges of an ice-free Lake Winnipeg

CGRG Bibliography of Canadian Geomorphology
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Abstract

Predictions of numerical hydrodynamical models of seiches, steady circulation, and water level setup and time-dependent motions known as storm surges were compared to limited amounts of water level data during the ice-free season on Lake Winnipeg.Two-dimensional gravitational seiches were computed by minimizing an expression for the total energy. The fundamental inviscid period is 39 h, which is considered to be a maximum for any inland water body. Four higher modes of oscillation were detected in spectra of water level fluctuations at three stations on Lake Winnipeg. Frictional effects were shown to have appreciable influences on the seiches. Predicted water level setup had an asymmetrical distribution, with the largest excursions occurring in the southern basin. A number of observations of water level setup were in accordance with model predictions at Winnipeg Beach if a drag coefficient of 0.001 is assumed. Setup is relatively insensitive to vertical eddy diffusivities in the range 10-100 sq cm/s. A modeling strategy utilizing the previously obtained solutions for the free oscillations and for the steady state setup resulted in a simple prediction scheme for arbitrary forcing in time involving the convolution of the time history of the wind stress components with the response of the lake. Predicted storm surges were in reasonable agreement with two storm surges measured at two locations in the southern basin, considering the imperfect knowledge of the forcing obtained from winds at a single station in the northern basin

Bibliography of Canadian Geomorphology