Towards a changed view on greenhouse gas exchange in the Arctic:New findings and improved techniques

• Main Author: Mastepanov, Mikhail
• Format: Book Part
• Language: English
• Published: 2010
• Subjects: Arctic; Carbon dioxide; Chamber; Fen; Greenhouse gas; Methane; Permafrost; Greenland; Svalbard; permafrost
• Online Access: https://pure.au.dk/portal/da/publications/towards-a-changed-view-on-greenhouse-gas-exchange-in-the-arctic(fc5ad59d-ef37-4a9c-85fd-469cf69847bf).html; http://www.scopus.com/inward/record.url?scp=77953012180&partnerID=8YFLogxK

Arctic ecosystems represent an important component in the global terrestrial exchange of greenhouse gases and energy with the atmosphere. In the changing climate, which is most pronounced in the Arctic, the possible scenarios of greenhouse gas exchange response should be seriously considered in predictive climate modelling efforts. As a prerequisite for this, detailed studies of key processes affecting greenhouse gas exchange in the Arctic are important, as well as monitoring of its current dynamics. However, the number of such studies, carried on in high Northern latitudes is significantly smaller than for lower latitudes, and within the existing studies there is a bias towards studying the growing season. The main aim of this study was to improve our process understanding of greenhouse gas exchange in the Arctic terrestrial ecosystems, including the processes taking place at low temperatures and outside the growing season. In order to achieve this some development in measurement techniques, such as automatic closed and flow- through chambers, adapted for monitoring CR 4 and CO 2 exchange under Arctic conditions, membrane diffusion probes to study subsurface profiles of these gases, laboratory techniques of low-temperature incubation and gas exchange studies on permafrost samples. During the studies, some novel results were obtained, such as on detailed multiseasonal CH 4 emission dynamics in a high Arctic fen, on late-season bursts of CH 4 and CO 2 at Greenland and Svalbard, and in relation to respiration and its origin in old permafrost. Four years of CR 4 emission monitoring data have shown that the exchange of this greenhouse gas under truly Arctic conditions is having some very special dynamics and different dominating controlling factors compared with conventional knowledge from lower latitudes. The patterns of growing season CH 4 emission are highly dependent on the snow melt date. The greatest variations in fluxes between the study years was observed during the first 30-40 days after snow melt. This variability could not be explained by common factors controlling methane emission at lower latitudes: temperature and water table position. Late in the growing season CH 4 emissions were found to be very similar between the study years, this despite large differences in ambient and climatic factors. In this study we try to explain these unusual patterns. Late-season bursts of CR 4 and CO 2 coinciding with soil freezing after growing season was observed and documented in North-Eastern Greenland. A similar burst of CO 2 at freezing time was documented on Svalbard. The accumulated emission during the freezing-season CH 4 burst was found to be comparable in size with the growing season emission. In the study we also make an attempt to explain this phenomenon. Finally samples of permafrost soils up to 500 thousands years old were found to contain living microorganisms of the same age, continuing methabolic activity and CO 2 production. In this study we try to explain this unique feature of permafrost inhabitants.