Author(s): Bin Cheng; Ting Qin; Lixin Wei; Anna Kontu; Henna-Reetta Hannula; Timo Vihma; Xiaomin Ye
Linked Author(s):
Keywords: No Keywords
Abstract: The formation of lake ice strongly depends on the heat exchange at the ice-water interface, the radiative and turbulent heat fluxes at the ice/snow surface, as well as on precipitation. In Northern Finland, snowfall is guaranteed for each winter season, so the lake ice is composed by columnar ice (ice formed via bottom growth) and granular ice (snow-ice, superimposed ice). The impact of air temperature and precipitation on lake ice formation is investigated. The meteorological measurements from Sodanlylaweather station, northern Finland was used as external forcing to run a snow and ice model (HIGHTSI) for a climatological period 1980/1981–2012/2013 (33 winter seasons). The inter-annual variations of meteorological measurements are large. The air temperature increasing trends (P< 0.05) for annual cycle (AC: 1 July–30 June) and freezing season (FS: 1Nov. –30 April) are 0.68°C/10yr and 0.78°C/10yr, respectively. The biggest temperature increasing trend was 2.1°C/10yr in December. The total precipitation in FS slightly increased (P> 0.05). The increasing of liquid precipitation (P< 0.05) in FS results from temperature warm up. The validations of modelled snow and ice parameters in lake Orajarvi (freeze up date, thickness, snow onset melting and breakup date) was limited to the available in situ data sets, but in general the results were in line with available observations and showed reasonable variations in response to the weather forcing. The ice thickness showed a decreasing trend (P< 0.05). The portion of modelled ice composition (columnar and granular ice) showed periodically variations in 80s (columnar dominate), 90s (equally important of columnar and granular ice) and new millennium (decreasing of columnar and increasing of granular ice). For few extreme mild winters, the modelled lake ice thickness was thin, which was coherent with the overall sea ice condition in the Baltic Sea indicating that the weather forcing is a primary driving force for the ice formation.
Year: 2014