Sensitivity of the stability of Scandinavian river flow regimes to a predicted temperature rise

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Abstract
A river flow regime, describing the average seasonal pattern of flow, reflects climatic and physiographic conditions in a basin. This average pattern can be stable, demonstrating the same seasonality in river flow from year to year, or unstable, when the flow regime alternates between a number of different seasonal patterns. Flow regime types have traditionally been used mainly for regionalization purposes. Being dependent on climate and physiography, seasonal flow regime patterns respond to changes in these two factors. In the context of a possible climate change, river flow regimes (both type and stability) can be used to test the sensitivity of this important river flow characteristic to a temperature rise. Such a sensitivity study is reported here on Norwegian runoff series modelled for three possible scenarios of a mean annual temperature rise in Scandinavia of +1°, +2° and +3°C and for different altitudes. The concept of entropy is applied to quantify the stability of the seasonal patterns. The study shows that the majority of seasonal flow regimes are very sensitive to the temperature rises studied. Regimes with a snowmelt source of flow formation become more unstable, while regime types with a rain source become more stable.