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

We have developed a numerical model to simulate the heat budget of a s hallow ice-covered midlatitude lake. New features include: snowmelt du e to rain, sediment heat transfer, formation of snow-ice, and variabil ity 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 t he ice and sediment interfaces. The absence of stratification allowed us to focus our attention on the heat fluxes across these interfaces r ather than the details of the thermal structure within the lake. Discr epancies between held observations and model predictions are accounted for by parameter uncertainties and expected observation error. Sedime nt 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 r adiation through the ice.