Methane dynamics associated with a small Arctic lake, southwest Greenland

Despite the abundance of small lakes in Greenland, there are few studies describing the CH4 dynamics associated with theses lakes. This study utilizes open-path laser (OPL) technology to assess the CH4 concentration in the atmosphere of a small lake in southwest Greenland and its relations to atmospheric variables (temperature, pressure, and wind speed). Potentilla Lake (informal name) is 8 m deep, has a surface area of 1.8 ha, and has a long axis of roughly 280 m. Atmospheric CH 4 concentrations in the vicinity of the lake were measured by three different instruments. Meteorological variables were measured with a Davis Vantage Vue meteorological station. Epilimnetic, metalimnetic, and hypolimnetic water samples were sampled with a Kemmerer. Soil pore-gasses were sampled with a soil-gas sampling probe. Atmospheric CH4 concentrations were not elevated compared to the NOAA predicted CH4 concentration for arctic regions (1.84 ppmv). Lake waters were always super-saturated with CH4 compared to water in equilibrium with atmospheric CH4 (1.236 ± .002 - 231 ± 12 μM). Lake sediments showed the highest CH4 concentrations of all the sub-environments studied (320,000 ± 16,000 ppmv). Dry, upland soils associated with a ridge always showed sub-atmospheric CH4 concentrations (0.09 ± 0.04 - 1.07 ± 0.17 ppmv), while the lowland soils showed both dry and wet microenvironments and exhibited both super-saturated and sub-atmospheric CH4 concentrations. Potentilla Lake did not exhibit "hot spot emissions" and showed similar rates of emission to other Boreal and Arctic lakes. Potentilla Lake and its catchment represent a complex environment with patches of methanotrophy (CH4 consumption) and methanogenesis (CH4 production). Despite local sources and sinks of CH4 in the vicinity of Potentilla Lake these sources were not strong enough to change the background mixing ratio of CH4 in the atmosphere surrounding Potentilla Lake.