Author(s): Juha Aaltonen; Noora Veijalainen; Mikko Huokuna
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Abstract: The winter discharges in northern rivers are estimated to increase significantly because of the climate change. This may lead to changes in frazil and anchor ice formation and frazil ice jams in rivers because those phenomena depend on discharge and weather conditions. This study utilizes a previous study in which the effect of the climate change on frazil ice problems in Kokemaenjoki River in Finland was presented. In this study the discharge scenarios for future time periods are simulated with the conceptual watershed model. The time periods used are 2010-2039 and 2040-69 along with the reference period of 1971-2000. Four climate scenarios from both global and regional climate models with the SRES A1B emission scenario are used together with the delta change approach. Unlike in the previous study, a modification to the basic delta change approach that includes a temperature dependant component is used. In this modification the changes in daily temperature are made based on seasonal linear transfer functions and depend on the reference period temperature. The monthly temperature changes are scaled to equal the change in the climate scenario. The results from the simulations of the hydrological and climate models include for example the average daily discharges and air temperatures are used to estimate the changes in frazil ice production. Based on the previous study a more sophisticated spreadsheet application is developed to estimate the changes in the probability of frazil ice formation. In this study the monthly heat flux from water to air during possible frazil ice formation period is also calculated. The total monthly energy flux from water to air during the frazil ice formation period is compared between the reference period and the climate change scenarios. The example area for this study is the middle part of the Kokemaenjoki River. The river which is located in Southwest Finland is known for harmful frazil ice floods.
Year: 2010