Environmental Change Research Unit - ECRU

Lake ice

LONG-TERM CHANGES IN LAKE ICE CONDITIONS IN NORTHERN FINLAND

Kone Foundation

Duration: 2007-2008

General discription:

Finland has some of the world's longest records concerning lake and river ice cover duration and thickness. Break-up dates of Tornionjoki River ice have been registered since 1693 and several other rivers have been monitored (but with many gaps in the data) since the 18 th century. Freezing and thawing of Lake Kallavesi have been recorded since winter 1821-1822, Lake Näsijärvi since winter 1835-1836, and Lake Oulujärvi since winter 1854-1855. Most records reaching back to the 19 th century are from Southern and Central Finland .

Ice cover records are considered to be even better indicators of past climate than temperature records. Direct human impact on ice phenology is very small, especially in Northern Finland . Several feedback processes (ice- and snow-albedo, thawing of permafrost, cloud formation) are operating in the northern areas, amplifying the global climate change. Warming will lead to longer and warmer ice-free season and increased nutrient and carbon input from the catchment areas. In response, the total primary production is likely to increase and species composition changes will take place.

During this project, the already existing ice cover records will be supplemented with new data, gathered from e.g. provincial archives, power plant companies, fishing clubs, road districts, newspapers and the general public. The role of ice cover length on phytoplankton biomass and species composition will be studied by sampling lakes situated along an altitude gradient in NW Finnish Lapland. In addition, paleolimnological methods will be utilized in order to reconstruct the past ice cover history of five subarctic lakes using diatom remains as proxy indicators.

The obtained ice-timeseries and paleo reconstructions will be combined using wavelet-analysis and further analysed with SiZer-techniques.

Objectives:

•  How big is the natural variation in the climate of Northern Finland ?

•  Does the variation of last decades exceed the natural long-term variation?

•  Is it possible to generate a comprehensive idea of the climate change and sensitivity of Northern Finland using ice conditions?

•  How does the ice phenology affect the dynamics and composition of aquatic (planktonic) organisms?

•  How does the climate change affect ice cover duration and ecosystems of Northern Finland in the future?

Expected results:

•  Statistically significant, comprehensive time series of ice cover duration and thickness of Northern Finland , going back several hundred years

•  More information on natural variation of climate and human impact on climate change

•  Knowledge on the effects of ice phenology on lake ecosystems

•  More information of the relationship between climate and ice cover duration during the Holocene

Project partners:

ECRU:

Prof. Atte Korhola

Ph.D. Laura Forsström

Ph. D. Jan Weckström

Finnish Environment Institute:

Ph.D. Esko Kuusisto

University of Oulu :

Prof. Lasse Holmström

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