Climate change, impacts and vulnerability in Europe ... - MemoFin.fr

Climate impacts on environmental systemsFigure 3.10 Trends in water temperature of large European rivers and lakes in the20th century°C25201510501900 1920 1940 1960 1980 2000Rhine, Lobith Danube, Vienna Meuse, EijsdenLake Saimaa, FinlandLake Võrtsjärv, EstoniaNote:Annual average water temperature in River Rhine and River Meuse (1911–2010); River Danube (1901–1998), Lake Võrtsjärv(1947–2011), and average water temperature in August in Lake Saimaa, Finland (1924–2011).Source: River Rhine and River Meuse: Compendium voor de Leefomgeving, 2012; River Danube: Hohensinner, 2006 (personalcommunication); Lake Saimaa: Johanne Korhonen, 2012 (personal communication); Lake Võrtsjärv: Peeter Nõges, 2012(personal communication).increase has been observed in the Meuse. The annualaverage temperature of the Danube increased byaround by 1 °C during the last century. Increases insurface water temperature were also found in somelarge lakes. Lake Võrtsjärv in Estonia had a 0.7 °Cincrease between 1947 and 2011, and the summer(August) water temperature of Lake Saimaa, Finlandincreased more than 1 °C over the last century.Several time series indicate a general trend ofincreasing water temperature in European riversand lakes in the range of 0.05 to 0.8 °C per decade(Dabrowski et al., 2004; George and Hurley, 2004;Pernaravièiûtë, 2004; Bresser et al., 2006). Thesurface water temperature of some rivers and lakesin Switzerland has increased by more than 2 °Csince 1950 (BUWAL, 2004; Hari et al., 2006). In thelarge lakes in the Alps the water temperature hasgenerally increased by 0.1–0.3 °C per decade: LakeMaggiore and other large Italian lakes (Ambrosettiand Barbanti, 1999; Livingstone, 2003; Annevilleet al., 2005; Dokulil et al., 2006).ProjectionsLake surface water temperatures are projectedto increase further, in parallel with the projectedincreases in air temperature. The exact amountof warming depends on the magnitude of globalwarming, on the region, on the season and onlake properties (Malmaeus et al., 2006; Georgeet al., 2007). Physical modelling studies predictthat temperatures will increase more in the upperregions of the water column than in the lowerregions, resulting in generally steeper verticaltemperature gradients and enhanced thermalstability (Peeters et al., 2002). Such increased lakethermal stability was observed both in Switzerlandduring the mild 2006/2007 winter (Rempfer et al.,2010) and in Italy during the hot 2009 summer(Nõges et al., 2011). Further impacts of increasedlake and river water temperature are described inSection 3.3.6.Climate change, impacts and vulnerability in Europe 2012123