Modelling of ice thermodynamics in natural water bodies

Abstract

A thermodynamic synoptic-scale sea-ice (freshwater lake) model was constructed for simulating ice thickness, ice temperature and air–ice interaction. The model includes calculation of the air–ice interface temperature and surface fluxes, as well as heat conduction in the snow and ice and heat flux and ice thickness variations at the ice–ocean boundary. Attention was given to the parameterization of the various fluxes, especially the radiative fluxes and in the calculation of the turbulent surface heat fluxes the effect of atmospheric stratification is taken into account. An iterative air–ice interface temperature serves as the key parameter controlling the surface heat balance, heat conduction and ice thickness variation at the upper surface. A conservative integral difference scheme is used to solve the heat conduction equation for an ice column consisting of 10 to 30 layers, normally in the vertical. In addition to thickness variations, the model yields the time development of the ice surface and in-ice temperatures and air–ice fluxes. The model is also able to generate the near-surface atmospheric profiles of wind, temperature and moisture. Model-calculated ice thickness and in-ice temperature variations were compared with observational data from the Bohai Sea and the Baltic Sea as a first step in verifying the model. Additionally, phenomenological process studies of subsurface melting and of the role of new snow above ice in spring is reported. The results indicate the atmospheric boundary layer (ABL) dynamically coupled with the ice and heat conduction in the ice as factors responsible for controlling ice growth, except under conditions of remarkable heat fluxes from the ocean. In the spring, the role played by shortwave radiation in the surface heat balance and extinction in ice are of primary importance and control the melting. After validation, the model should be applicable and suitable for ice thermodynamics studies, for coupled air–ice–ocean models and even for climatic scenarios.