Heat budget of lake ice during a complete seasonal cycle in lake Hanzhang, northeast China

The seasonal cycle of ice formation and breakup in Lake Hanzhang, China, was monitored during the winter of 2020-2021 using a float equipped with meteorological, hydrological, and optical instruments. This lake is located in mid-latitude cold and dry climate zone. We categorized the ice season into growth, equilibrium, and melting stages. The thickness of ice increased by an average of 0.7 cm day(-1) at the bottom of the ice during the growth stage, and during the equilibrium stage it was stable at 35.0 +/- 0.5 cm. During the melting stage, the internal melting dominated the ice ablation (1.0 cm day(-1)), followed by bottom melting (0.45 cm day(-1)) and surface melting (0.25 cm day(-1)). The net short-wave and long-wave radiative fluxes dominated the heat budget throughout the seasonal cycle. Sublimation was 1.1 cm, 73% of that in the growth stage. During the melting stage, the absorbed short-wave radiative flux promoted internal melting, enlarged the porosity, and enhanced further surface melting. The frequent negative air temperature during nighttime hindered the phase changes of the lake ice surface layer. In addition, the upward sensible heat flux in the lake water body increased from 7.8 to 14.5 W m(-2) due to the increased light transmittance by lake ice. The heat balance and heat fluxes in ice-covered lakes in mid-latitude dry climate have rarely been explored. The results increase the knowledge of lake ice geophysics and are also useful for calibration and validation of lake ice models.