Spatiotemporal hydroclimate variability in Finland: Past trends

Over the past decades, Finland has experienced changes in its climate: temperature and precipitation have increased, resulting in varying runoffpatterns. These trends are well studied, but the changes in interannual variability are less known, despite their importance for understanding climate change. This research aims to assess spatiotemporal changes in variability of temperature, precipitation, and runofffor 1962-2014 at the subbasin scale in Finland. Temporal changes in variability were analyzed by constructing moving-window median absolute deviation time series at annual and seasonal scales. Subbasins with similar patterns of temporal variability were identified using principal component analysis and agglomerative hierarchical clustering. Presence of monotonic trends in variability was tested. Distinct areas with similar patterns of statistically significant changes in variability were found. Decreases in annual, winter, and summer temperature variability were discovered across Finland, in southern Finland, and in northern Finland, respectively. Precipitation variability increased in autumn in northern Finland. It also decreased in winter and spring in northern and central parts of Finland. Runoffvariability increased in winter in most parts of Finland and in summer in the central parts, but decreased in spring in southern Finland. Comparison with existing studies illustrates that trends in mean climate and its variability do not necessarily match, highlighting the importance of addressing both aspects. The findings of this study provide new information on hydroclimatic variability in Nordic conditions and improve the possibility to adapt and predict the changes in hydroclimatic conditions, including weather extremes.