Effects of changing climate on the hydrology of a boreal catchment and lake DOC - probabilistic assessment of a dynamic model chain

Uncertainty in future climate projections is widely recognised, yet few impact model studies explore the implications of this uncertainty on catchment hydrological and biogeochemical responses. Here, we report a novel model chain using HBV, INCA-C and MyLake to simulate runoff, snow dynamics, ice cover, soil moisture, lake thermal stratification and in-lake DOC concentrations in Valkea-Kotinen, a headwater lake in a forest-covered boreal catchment. Impact response surfaces (IRSs) were constructed with 63 combinations of changes in temperature (-2 degrees C to +14 degrees C) and precipitation (-10% to +50%). Superimposing probabilistic projections of climate change onto the IRSs, we illustrate the uncertainty in impacts under projected climate change. Projected climate warming is likely to result in drier soils, shorter snow and ice periods, as well as earlier onset and longer duration of lake stratification. In contrast to earlier results, in-lake DOC concentrations are projected to decrease slightly (-6%), primarily due to decreased terrestrial runoff.