, Volume 322, Issue 1-3, pp 91-97

Mixing in ice-covered lakes

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Abstract

Mixing in ice covered lakes is caused by through-flow currents, oscillations of the ice cover and by convective currents induced by heat flow from the sediments or by solar radiation penetrating the ice. Mainly from studies in Swedish lakes, current velocities and mixing coefficients are quantified for the different processes generating water movement. Seiche movement caused by wind induced oscillations of the ice cover is found to be most efficient for the horizontal mixing giving coefficients of the order 100 cm2 s−1. The lateral dispersion in through-flow currents can be determined using standard formulas, but the dispersion coefficient is 1–2 orders of magnitude less than that for oscillation induced mixing. Convective mixing due to heat flow from the sediments lasts through the winter but is a very slow process. Convection caused by penetration of solar radiation is more effective, but this process is usually of importance only during the last month prior to break-up of the ice-cover.