Extreme Climate Effects on Dissolved Organic Carbon Concentrations During Snowmelt

Extreme weather and climate events are predicted to increase in frequency and severity in the near future, which could have detrimental consequences for water quality in northern latitudes. Key processes that regulate the production and transport of solutes, like dissolved organic carbon (DOC), from soils to streams can be potentially altered by episodes of extreme temperature and/or precipitation. Here we use an intensively studied research catchment in northern Sweden with 23 years of data to ask how extreme antecedent climate events influence DOC concentration during snowmelt. Specifically, we used a combination of principal components analysis, cluster analysis, and multivariate partial least square analysis to show that almost every year provides some combination of extreme conditions in terms of intensity, duration, or frequency of temperature and/or rainfall. However, in terms of DOC responses to these events, variations in peak concentrations were most closely related to cold winter conditions, winter precipitation (snow), and temperature during the previous autumn. Specifically, years with most severe frost and icing during winter, but low winter precipitation, previous summer precipitation, and warmer autumns, showed the highest peaks in concentrations. In contrast, the lowest peak DOC concentrations were observed during spring snowmelt following high summer precipitation, colder autumns, and high winter precipitation. While this research highlights the importance of winter climate for influencing the DOC concentration during the spring, it also points to the potential importance of lag effects from preceding seasons on responses observed during the snowmelt season.