Sammendrag
The aim of this project was to provide historical and future changes in organic carbon (OC) for Farrisvann using sediment reconstructions and simple modelling tools. Sediment cores were taken from the lake in 2016 and dated using Pb dating, attempts were made to reconstruct historical OC (VNIRSmethod)
but sediment geochemistry showed that redox reactions controlled the sediment profile and OC reconstructions could not be trusted.
We used data from another Norwegian lake, long-term monitoring data available for Farrisvann and the most novel scientific knowledge to the model future changes in OC concentrations until 2050. We predicted the future changes in OC using different scenarios based on historical sediment reconstructions, monitoring data, and scientific literature.
We predict that concentrations of OC in Farrisvann could continue to increase at the same rate as the monitoring data has shown due to increases in precipitation predicted by the climate models for Norway. It is unlikely that a combined acidification and climate signal will drive OC concentration in the future as the recovery from acidification has been substantial. As we were not able to reconstruct historical OC for Farrisvann, we cannot estimate how much OC changed during acidification. We recommend the water treatment plants to expect further increases and browner waters in Norway in the future.
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