Predicting summer surface water temperatures for large Austrian lakes in 2050 under climate change scenarios

Abstract

Long-term data on surface water temperature (SWT) from 9 lakes larger than 10 km2 located in different climatic regions in Austria were analysed for June-September 1965-2009. The lakes are situated north and south of the Alps, in the east bordering Hungary and in the west bordering Germany. Time series of air temperature (AT) and SWT were smoothed by the lowess function and linear trends. Water temperature for the year 2050 was estimated from (1) linear extrapolation of the time trend, (2) projection of the AT-SWT relation and (3) increase of average present day SWT (2000-2009) by 3°C in summer in the Alps as expected from models by climatologists. Results indicate a rise in SWT parallel to AT since the mid-1960s. On an annual basis, changes in water temperature were the greatest in spring and summer. A conservative estimate of the average increase of summer SWT until 2050 is 2°C (1.2-2.9°C), differentiated by region. As a consequence of warming water temperatures, the duration of thermal stratification will increase and mixing and retention time will be affected. Changes in the food web are difficult to forecast, but will strongly depend on local environmental conditions and will therefore be different for individual lakes. © 2013 Springer Science+Business Media Dordrecht.