Methods of hydrophysical measurements at autonomous stations in shallow lakes during the ice-covered period

Abstract

The article provides a brief description of some methods of hydrophysical measurements at autonomous stations in shallow lakes during the ice-covered period. These methods were designed based on 30 years of experience. Long-term records of solar radiation fluxes on the lake surface and at several depths inside the water column help identify patterns in the evolution of the snow-and-ice cover optical properties and water such as the albedo, and extinction coefficient (weakening) of the solar radiation fluxes in snow, white and black ice and water. Long-term measurements of water temperature by sensors distributed throughout the water column can be used to determine the start dates and duration of the annual thermal cycle stages, calculate the stability parameters of the water column, and characterize the mixing regime of lakes. Long-term measurements with dissolved oxygen sensors allow studying the daily, synoptic, seasonal and interannual variability of oxygen conditions in lakes in order to estimate the duration and severity of oxygen deficiency periods. Temperature measurements by sensors frozen into ice or positioned in water under ice allow estimating the heat flux at the water-ice interface and calculating the rate of black ice growth. An “Autonomous device for measuring the temperature profile in the bottom layers of water and soil” is used to study the dynamics of the heat flux at the water-sediment interface during the winter, including the poorly studied periods of ice formation and destruction. Measurements with current profilers are used to estimate the turbulence parameters of the mixed/stratified layers of ice-covered lakes in diurnal and synoptic cycles. The results of calculating the energy parameters (basic potential energy, buoyancy flux) of the water column of a small ice-covered lake are given to showcase the application of methods for measuring water temperature and solar radiation fluxes and assessing the mixing efficiency in the study of radiation-driven convection in ice-covered lakes.