| Summary: | Ice in natural waters grows and decays as forced by the fluxes through the upper and lower boundaries. In particular, the flux at the lower boundary -- i.e. the heat flux from the liquid water body into the bottom of the ice sheet -- is not very well known quantity. This question is approached by measurements and mathematical modelling. The data are from Saroma-ko lagoon, a saline lake on the northern coast of Hokkaido, and Lake Pääjärvi, a fresh water basin in southern Finland. Three-dimensional current velocity, temperature and salinity were measured at a fixed depth, and the resulting heat flux was normally 5-10 W/m2 in both basins, a bit more in Saroma. But even in Lake Pääjävi, which is a rather quiet water body in wintertime (total ice coverage with very weak currents) the heat flux from the water is important in the heat budget of the ice sheet. A three-layer (snow/snow-ice/congelation ice) model is used to examine the evolution of ice thickness and temperature. The 18th IAHR International Symposium on Ice. 28 August - 1 September 2006. Sapporo, Japan.
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