Abrupt changes in air temperature and precipitation: Do they matter for water chemistry?

We analyzed 120 years long time series of air temperature and precipitation from 29 respective 44 sites distributed all over Sweden and determined abrupt changes by using three methods. For air temperature we found significant changes in 1930 and 1989 and for precipitation in 1920, 1979, and 1998. Analyzing more than 30 yearlong time series of ice cover (333 sites), discharge and watercourses chemistry (87 sites), we observed abrupt changes in 1977, 1989, and 1998 for discharge but first in 1998 for watercourses chemistry, most pronounced for organic matter and sulfate concentrations. We suggest that the abrupt increase in air temperature in 1989 liberated more easily mobilized organic matter in the catchments, which, for water chemistry, was first detected in 1998 as a consequence of increased discharge. We conclude that increases in air temperatures can make ecosystems more sensitive to further changes in precipitation.