OBSERVATIONS AND NUMERICAL-SIMULATION OF A SHALLOW ICE-COVERED MIDLATITUDE LAKE

We have developed a numerical model to simulate the heat budget of a shallow ice-covered midlatitude lake. New features include: snowmelt due to rain, sediment heat transfer, formation of snow-ice, and variability in snow density, snow conductivity, and albedo. To test this model we conducted a field study of a shallow, midlatitude lake where there was no thermal stratification in winter beyond that associated with the ice and sediment interfaces. The absence of stratification allowed us to focus our attention on the heat fluxes across these interfaces rather than the details of the thermal structure within the lake. Discrepancies between held observations and model predictions are accounted for by parameter uncertainties and expected observation error. Sediment heat transfer may be important in early winter in preventing a net loss of heat from the lake water. Significant heat gains in the latter part of winter, however, are attributed to the penetration of solar radiation through the ice.