Abstract
Snow and ice thermodynamics was simulated applying a one-dimensional model for an individual ice season 2008–2009 and for the climatological normal period 1971–2000. Meteorological data were used as the model input. The novel model features were advanced treatment of superimposed ice and turbulent heat fluxes, coupling of snow and ice layers and snow modelled from precipitation. The simulated snow, snow–ice and ice thickness showed good agreement with observations for 2008–2009. Modelled ice climatology was also reasonable, with 0.5 cm d−1 growth in December–March and 2 cm d−1 melting in April. Tuned heat flux from water to ice was 0.5 W m−2. The diurnal weather cycle gave significant impact on ice thickness in spring. Ice climatology was highly sensitive to snow conditions. Surface temperature showed strong dependency on thickness of thin ice (<0.5 m), supporting the feasibility of thermal remote sensing and showing the importance of lake ice in numerical weather prediction. The lake ice season responded strongly to air temperature: a level increase by 1 or 5°C decreased the mean length of the ice season by 13 or 78 d (from 152 d) and the thickness of ice by 6 or 22 cm (from 50 cm), respectively.
Highlights
Freshwater lakes cover about 2% of the Earth’s land surface
If we look into the average situation, we can see that the surface temperature dependence on ice thickness is more pronounced for ice thickness B0.5 m, as noted by Lepparanta and Lewis (2007)
The ice cover in Lake Vanajavesi has been investigated with a one-dimensional thermodynamic model HIGHTSI
Summary
Freshwater lakes cover about 2% of the Earth’s land surface. 190 000 lakes larger than 500 m2, accounting for 10% of the area of the whole country, and these lakes freeze every winter. Their ice sheets consist of congelation ice and snowÁice with snow cover normally on top. In medium-size and small lakes, the ice cover is usually stable, while in large lakes mechanical displacements may take place, creating piles of ice blocks or ridges. An ice cover stabilises the thermal structure of a lake. Ice sheets gain heat mainly from solar radiation, and as the ice melts, all impurities contained in the ice are released into the water or to the air
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