Author(s): G. B. Kirillin; I. A. Aslamov; V. V. Kozlov; N. G. Granin; C. Lhardt; J. Forster
Linked Author(s): Georgiy Kirillin
Keywords: No Keywords
Abstract: The vertical heat and mass transport across the water-ice boundary layer strongly affects growth and melting of the lake ice. The existing models of ice cover dynamics focus basically on the dependence of the ice thickness on the air temperature with implicit account of the effect of snow cover. The heat flux at the water-ice boundary, in turn, is usually neglected or parameterized in a very simplistic form. However, neglect of the basal ice melting due to heat flux at the icewater interface produces appreciable errors in the modeled lake ice phenology. We analyze fine-structure observations taken in spring 2014 in ice-water boundary layers of Lake Baikal and arctic Lake Kilpisj"arvi (northern Finland) to reveal the major physical drivers of the heat exchange at the ice bottom and to explain the high geographical, spatial, and temporal variability in the heat flux magnitudes. The new data provide first detailed estimations of the heat exchange beneath the ice cover, available previously only from bulk estimations. The fluxes in Lake Baikal have magnitudes of 10 Wm and vary strongly between different parts of the lake being influenced by large-scale horizontal circulation with current velocities amounting at 5-7 cm s. The shallow lake fluxes, while an order of magnitude weaker, arestrongly non-stationary, affected by the turbulence due to oscillating currents under ice. Our results demonstrate the role played by the boundary layer mixing in the ice growth and melting, as well as characterize the physi cal processes responsible for the vertical heat exchange and provide a basis for an improved parameterization of ice cover in coupled lake-atmosphere models.