Temperature-Dependent Methanotrophy in High Arctic Permafrost: Implications for Global Warming

Abstract

As global temperatures continue to rise, more and more permafrost within the high Arctic thaws each year. Given that permafrost is one of the largest terrestrial soil organic carbon (SOC) reservoirs, it is imperative that we understand how this environment will react to rising global temperatures in the coming decades. Previous global climate models have indicated that rising temperatures in the Arctic would lead to increased methanogenesis and ultimately raise the atmospheric concentration of CH4; however, few studies have noted that the active layer of soil in the High Arctic may serve as a CH4 sink. As the climate continues to change, areas in the high Arctic will be subjected to warmer temperatures as well as increased rainfall. The effects of increased water saturation as well as temperatures have not been modeled. The purpose of this study is to study the effects of changes in temperature and water saturation throughout the active layer and permafrost collected from Axel Heiberg Island and to improve upon methods utilized in previous studies. The results indicated enhanced levels of methanotrophy within the top 10cm of the active layer at 33% saturation and 10°C. The calculated flux for CH4 in this condition was -1.54 mg/m2/day which is comparable to results reported in previous studies. This flux was significantly lower than fluxes reported in areas with high rates of methanogenesis; however, these areas only account for a much smaller portion of total permafrost land mass. Overall, the results from this study demonstrated that the rates of methanotrophy in high Arctic soil will increase drastically in warmer temperatures; however, added water to the system negates the rate increase from increased temperatures and can lead to situations where the material is no longer a CH4 sink.