Methane and Carbon Dioxide Dynamics in Arctic Lake Sediments

Abstract

Rising global temperatures are expected to increase concentrations of greenhouse gases emitted by northern latitudes within the current century. The impact of global warming on Arctic lacustrine systems is generally unknown, although recent studies have examined fluxes of carbon dioxide (CO₂) and methane (CH₄) produced in ebullition events. Few studies have investigated the added impact of atmospheric warming on lake sediments, which produce CO₂ and CH₄ through microbial decomposition and diffusive loss in the water column. To better understand carbon emission scenarios at elevated temperatures, sediment samples from Abisko, Sweden were analyzed for CO₂ and CH₄ production rates through incubation studies, and for concentrations of dissolved inorganic carbon (DIC) and dissolved CH₄ in sediment and porewater. Results showed that room temperature incubations emitted concentrations of CO₂ and CH₄ up to five times greater than those emitted by +5°C incubations. Furthermore, documented peat emissions were one to two orders of magnitude lower than the lake sediment incubation emissions reported in this paper. This study provides some of the first point source microbial emissions by lake sediment depth, and highlights that northern latitude sediments could have unprecedented effects on current spatial and temporal projections of Arctic warming.