Radiation transfer and heat budget during the ice season in Lake Pääjärvi, Finland

Abstract

Lake Pääjärvi, a boreal Finnish lake, was investigated in winter for weather conditions, structure and thickness of ice and snow, solar radiation, and under-ice current and temperature. Heat budget of Lake Pääjärvi in January-March was governed by terrestrial radiation losses of 20-35 W m -2 recompensed by ice growth of 0.5-1.0 cm day -1 . In April, snow melted, albedo decreased from 0.8 to \0.1, and the mean ice melt rate was 1.5 cm day -1 . Internal melting and surface melting were about equal. The mean turbulent heat loss was small. The heat flux from the water to ice was about 5 W m -2 in winter, increasing to 12 W m -2 in the melting season. The light attenuation coefficient was 1.1 m -1 for the congelation ice (black ice) in winter, compared with 1.5 m -1 for the lake water, and it was up to 3 m -1 for candled congelation ice in spring, and about 10 m -1 for superimposed ice (white ice) and snow. Gas bubbles were the main factor that reduced the transparency of ice. The radiation penetrating the ice heated the water body causing convective currents and horizontal heat transfer. This increased the temperature of the water body to about 3°C before the ice break-up. After the snow had melted, the euphotic depth (the depth of 1% surface irradiance) was estimated as 2.0 m, only two-thirds that in summer.

Changeability of Accumulated Heat Content in Alpine-Type Lakes

“…The increasing heat accumulated in the water of Morskie Oko has also resulted in shorter ice cover duration - [29] assessed as having decreased by 10 days·dec -1 . The relationship between heat content and ice cover has been described in the example of Lake Pääjärvi in southern Finland [30]. Those data might be useful for further studies on processes determining lake dynamics.…”

Modeling the impediment of methane ebullition bubbles by seasonal lake ice

“…During this period, vertical melt channels spanning the ice layer form between black ice crystals with horizontal c axes and tend to grow larger as melt progresses, facilitating the transport of water and trapped gas (Browman, 1974). The absorption of solar radiation within the ice layer accelerates this process, particularly after the high-albedo snow cover has melted completely (Williams, 1969;Ashton, 1986;Jakkila et al, 2009), as does the presence of ice-trapped bubbles (our observation when harvesting ice blocks; A. Bondurant, personal communication, 2014).…”

“…(2) and (3) are invalid for T air > 0, which was the case on 4 consecutive days in October 2010 after freeze-up, but we applied this model as an approximation. Previous studies of melting ice found the formation of channels within lake ice instead of decreasing thickness (e.g., Browman, 1974;Nye, 1989;Jakkila et al, 2009), so we assume zero ice growth around trapped bubbles during this period.…”

Numerical modelling of snow and ice thicknesses in Lake Vanajavesi, Finland

“…The heat flux from lake water to the ice bottom has been earlier examined in the nearby Lake Pa¨a¨ja¨rvi by Shirasawa et al (2006) and Jakkila et al (2009). The magnitude was found to be 3Á10 W m (2 based on field data.…”