Modeling experiments on seasonal lake ice mass and energy balance in Qinghai-Tibet Plateau: A case study

Abstract. The lake-rich Qinghai-Tibet Plateau (QTP) has significant impacts on regional and global water cycles and monsoon systems through heat and water vapor exchange. The lake-atmosphere interactions have been quantified over open-water periods, yet little is known about the lake ice thermodynamics and heat and mass balance during ice-covered season due to a lack of field data. Modeling experiments on ice evolution and energy balance were performed in a shallow lake with a high-resolution snow and ice thermodynamic model. The bottom ice growth and decay dominated the seasonal evolution of the thickness of lake ice. Strong surface sublimation was a crucial pattern of ice loss, which was up to 40 % of the maximum ice thickness. Simulation results matched well with the observations with respect to ice mass balance components, net ice thickness, and ice temperature. Strong solar radiation, consistent freezing air temperature, and low air moisture were the major driving forces controlling the seasonal ice mass balance. Energy balance was estimated at the ice surface and bottom, and within the ice interior and under-ice water. Particularly, almost all heat fluxes showed significant diurnal variations including short- and long-wave radiation, turbulent heat fluxes, water heat fluxes at ice bottom, and absorbed and penetrated solar radiation. The calculated ice surface temperature indicated that the atmospheric boundary layer was consistently stable and neutral over the ice-covered period. The turbulent heat fluxes between the lake ice and air and the net heat gain by the lake were much lower than those during open-water period. Ice surface sublimation (vapor flux) was demonstrated to be a vital seasonal water balance component, accounting for 41 % of lake water loss during the ice seasons.