Modelled impact of climate change scenarios on hydrodynamics and water quality of the Rävlidmyran pit lake, northern Sweden

Predictive modelling for three climate scenarios, based on the three greenhouse gas emission scenarios RCP 2.6, RCP 4.5 and RCP 8.5, was conducted for the Rävlidmyran pit lake, located in Västerbotten, northern Sweden. The model output for pH, temperature, dissolved oxygen, Cl, Fe3+, and Zn during the 10-year period 2090–2099 was compared to the model output during the 10-year period 2006–2015, for which measured meteorological data was used as input. Changes in thermocline, chemocline and water outflow were also evaluated. The results indicate that the water outflow from the pit lake will increase, as well as the number of days when the temperature in the mixolimnion exceeds 12 °C. The largest changes are seen for the highest greenhouse gas emission scenario (RCP 8.5). A small increase in Zn outflow (4.4%) could be observed for the RCP 8.5 emission scenario compared to the RCP 2.6 scenario. The results also indicate that the stratification of the lake is relatively stable, and it is predicted to remain meromictic for all climate scenarios. However, a sensitivity analysis indicates that a reduction of groundwater inflow element concentrations by 25–50% may result in a weakened stratification of the lake. Minor dilution could be observed in the monimolimnion of the lake as the modelled Cl concentration decreased by ∼0.3 mg/L in the RCP 8.5 emission scenario compared to the 2006–2015 period. The Cl concentration was also lower in the RCP 8.5 scenario compared to the RCP 2.6 and RCP 4.5 scenario, both in the mixolimnion and the monimolimnion.