Modeling the Ice Mass and Heat Budget in Shallow Central Asian Lakes With Focus on Ice–Water Interaction

Abstract

A key challenge in lake ice modeling is quantifying the heat flux from water to ice. In shallow Central Asian lakes, where the seasonal ice cover mainly consists of columnar congelation ice, sunlight penetration enables strong interactions between ice and water. The evolution of ice cover in Lake Ulansu (Ulansuhai, Wuliangsuhai) in northern China was investigated via the High-resolution Thermodynamic Snow and Ice (HIGHTSI) model. Atmospheric forcing was provided by calibrated ERA5 reanalysis data, and the initial freeze-up dates were identified from remote sensing observations. A new parameterization of the water–ice heat flux (F_w), which is suitable for shallow lakes, was proposed as F_w = aQ_sw + b, where Q_sw represents the solar heating of water and a and b are fitted coefficients. The model showed high correlations (>0.9) and low errors (<5 cm for ice thickness; <2°C for ice temperature) with respect to field observations. Throughout the ice season, long- and shortwave radiation promoted ice growth and melting, respectively. Surface melting and sublimation accounted for 9.5% and 9.8%, respectively, of the total ice decay, and the water–ice heat flux F_w = −17.5 ± 13.0 W m⁻² was critical for simulation accuracy. Furthermore, despite the shallow depth, the lake released over 100 W m⁻² of heat into the atmosphere for 2 days after break-up. These findings highlight the climatic sensitivity and support sustainable water resource management of more than 10,000 shallow lakes in Central Asia.