Mellersta Harrsjön

Mellersta Harrsjön is a 1.1 ha lake with a mean depth of 1.9 m and a maximum depth of 6.7 m. It is located in the Stordalen Mire, a peatland permafrost complex characterized by thawing permafrost in northern Sweden. The lake is not a thermokarst feature but instead formed after the last deglaciation. The sediments of the lake are organic-rich - mostly from internaly produced detritus - and produce large quantities of methane (Wik et al., 2018, doi:10.1029/2017JG004298). The lake is fed by a mountain stream which results in elevated concentrations of CO2 compared to other lakes on the Mire (Lundin et al., 2013, doi:10.1002/jgrg.20092). Long-term high-resolution measurements include water temperature profiles (2009-2019) as well as dissolved oxygen and specific conductivity (2015-2019). Manual observations include fluxes of methane (bubble traps and floating chambers) and carbon dioxide (gas transfer model) to the atmosphere and concentration profiles and stable isotope measurements of the same during the ice-free season as well as under-ice (Jansen et al., 2019, doi:10.1029/2019JG005094).