Importance of West Siberian Peatlands to Global Carbon and Water Cycles

Abstract:

Russia’s West Siberian Lowland (WSL) contains nearly 600,000 km² of peatlands with depth >0.5 m, the most extensive such deposits in the world. These peatlands impact the global carbon cycle, representing an important CH₄ source and net CO₂ sink since the early Holocene. However, together with other Arctic and sub-Arctic peatlands, the likely responses of WSL peatlands to warming climate and associated permafrost degradation are a subject of ongoing study and debate. Of prime interest is whether WSL peatlands may switch from a net carbon sink to source, especially in permafrost peatlands. Climate models predict warmer temperatures, longer growing seasons, and enhanced precipitation which should increase net primary productivity and litter production, but also soil microbial decomposition, increasing release of sequestered carbon through outgassing of CH₄ and/or CO₂ to the atmosphere. Projecting the net outcome of these opposing ecosystem processes on carbon sink/source status requires is difficult, and given strong N-S temperature and permafrost gradients across the WSL, the response will likely vary geographically. Hydrological status is deeply important because aerobic dry peats emit a greater fraction of CO₂ whereas anaerobic wet peats predominately release CH₄. A first estimate of subsurface water storage in WSL peatlands suggests they may hold ~1,200 km³ of liquid-water equivalent (~2 m), a large number that is roughly triple the annual flow of water in the Ob’ River. New models, observations, and synthesis are needed to confidently project the future role of this important region to global carbon and water cycles.