A floating remote observation system (FROS) for full seasonal lake ice evolution studies

A floating remote observation system (FROS) was designed to investigate the full seasonal evolution of lake ice. FROS operates effectively in open water and ice. It can automatically measure meteorological data, such as the air temperature and solar radiation, as well as ice/snow data, including ice thickness and snow depth. These observations help to fill the current knowledge gap of lake ice observations during the early freezing and late melting periods because of the limited bearing capacity of ice cover. A mid-latitude lake was selected for field experiments to verify the effectiveness of FROS, where the duration of the survey was 101 days, of which 97 were during an ice-covered period. The results reveal that the lake ice went through a fast freezing period, equilibrium period, and a melting period, with a maximum ice thickness of 35.5 cm. The ice melting rate was 1.7 cm/day, which was approximately double the ice growth rate of 0.7 cm/day during the fast freezing period. FROS was able to record the complete evolution of lake ice and of different meteorological elements, with good stability in both open water and frozen conditions, and can accommodate wind speeds up to 6.4 m/s. Meanwhile, FROS has good versatility, and other measurement instruments such as chlorophyll and dissolved oxygen sensors, long wave radiometers, and conductivity sensors can be added to it. The application of FROS will be important for calculations of the thermal balance of snow and ice, and studies of the annual and seasonal evolution of ecological characteristics in frozen lakes.