Abstract
Abstract. A one-dimensional process-based multi-year lake ice model, MyLake, was used to simulate lake ice phenology and annual maximum lake ice thickness for the Nordic region comprising Fennoscandia and the Baltic countries. The model was first tested and validated using observational meteorological forcing on a candidate lake (Lake Atnsjøen) and using downscaled ERA-40 reanalysis data set. To simulate ice conditions for the contemporary period of 1961–2000, the model was driven by gridded meteorological forcings from ERA-40 global reanalysis data downscaled to a 25 km resolution using the Rossby Centre Regional Climate Model (RCA). The model was then forced with two future climate scenarios from the RCA driven by two different general circulation models (GCMs) based on the Special Report on Emissions Scenarios (SRES) A1B. The two climate scenarios correspond to two future time periods namely the 2050s (2041–2070) and the 2080s (2071–2100). To take into account the influence of lake morphometry, simulations were carried out for four different hypothetical lake depths (5 m, 10 m, 20 m, 40 m) placed at each of the 3708 grid cells. Based on a comparison of the mean predictions in the future 30-year periods with the control (1961–1990) period, ice cover durations in the region will be shortened by 1 to 11 weeks in 2041–2070, and 3 to 14 weeks in 2071–2100. Annual maximum lake ice thickness, on the other hand, will be reduced by a margin of up to 60 cm by 2041–2070 and up to 70 cm by 2071–2100. The simulated changes in lake ice characteristics revealed that the changes are less dependent on lake depths though there are slight differences. The results of this study provide a regional perspective of anticipated changes in lake ice regimes due to climate warming across the study area by the middle and end of this century.
Highlights
According to the European Environmental Agency (EEA), there are more than 500 000 natural lakes larger than 0.01 km2 (1 ha) in Europe, and three quarters of the lakes are located in Norway, Sweden, Finland and the Karelia–Kola part of Russia (EEA database, 2012)
The simulations were carried out using Regional Climate Model (RCA) downscaled ERA-40 reanalysis data focussing on ice phenology and ice thickness
The delay in break-up using the ERA-40 data can be explained in part by the cold bias of the ERA-40 data compared to observed temperatures
Summary
According to the European Environmental Agency (EEA), there are more than 500 000 natural lakes larger than 0.01 km (1 ha) in Europe, and three quarters of the lakes are located in Norway, Sweden, Finland and the Karelia–Kola part of Russia (EEA database, 2012). Lake ice phenology (freeze-up date, break-up date and ice cover duration) and ice thickness are regarded as a good proxy for the past and present climate (Magnuson et al, 2000); in some cases it can be considered a more robust measure of climate variability and change than air temperature (Livingstone, 1997). Changes in lake ice cover characteristics due to anthropogenic causes will have significant ecological, hydrological and socioeconomic impacts (Prowse et al, 2011). This concern has increased as the analysis of historical lake ice observations indicates significant changes in the timing and duration of the ice season that is commensurate with global warming. From 1846 to 1995, average freeze-up dates were delayed by 0.58 days per decade, while break-up occurred 0.65 days earlier per decade. Benson et al (2011) updated the study by Magnuson et al with more lakes and more recent data
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