18. Greenhouse Gases and Energy Fluxes at Permafrost Zone

Energy, water, and greenhouse gas exchange in the permafrost zone play an important role in the regional and global climate system at multiple temporal and spatial scales. High-latitude warming in recent years has substantially altered ecosystem function, including biosphere–atmosphere interaction, which may amplify or dampen future high-latitude warming through a variety of feedback processes. In this chapter, we have reviewed the current state of energy, water, CO₂, and CH₄ exchange at the northern high-latitude permafrost zone, with synthesizing observed micrometeorological fluxes. Tundra has a higher summer and winter albedo with a longer snow period than boreal forests, resulting in that tundra less transfers sensible and latent energy to the atmosphere. Growing season length determines the spatial variability of the annual gross primary productivity and net growing season CO₂ sink. In contrast, interannual variabilities of the annual CO₂ budget at boreal forests are determined by ecosystem respiration, indicating an importance of ecosystem respiration in the boreal forests. The CO₂ fertilization effect could be an important determinant of the long-term greenhouse gas budget at sites with a near neutral CO₂ budget. In terms of annual greenhouse gas budget, CH₄ emission is more important than CO₂ budget for both boreal forest and Arctic wet tundra. Based on this synthesis, finally, we discuss future possible directions of study to reach a better understanding of changing high-latitude ecosystems, by synthesizing tower flux measurements in Alaska and Siberia and combining these in situ measurements with remote sensing data.