Potential springtime greenhouse gas emissions from a small southern boreal lake (Keihäsjärvi, Finland)

Concentrations of dissolved greenhouse gases (GHGs) methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) were investigated in a small southern boreal lake during the late winter ice-cover in 2000, 2001 and 2002. Potential emissions of these gases to the atmosphere at ice melt were estimated from their concentration profiles in the water column under ice during winter. The concentrations of CH4, CO2 and N2O increased with the depth, but the year-to-year variations were low. Carbon dioxide contributed to 99% of the global warming potential (GWP) of the total springtime GHG emissions which ranged from 103 to 128 g CO2-equivalents m–2. The results indicated that these kinds of northern mesotrophic lakes are not important sources of CH4 and N2O, but are probably significant sources of CO2.