Greenhouse gases research
Greenhouse gas group’s research has three different focus areas:
Accurate ambient air concentration measurements are the basis in following trends and in estimation of regional sources and sinks. These are done by atmospheric transport and biogeochemical models which use also remote sensing data. Micrometeorological flux measurements are conducted to observe carbon dioxide sinks and sources of forests, wetlands and fields and methane emissions from wetlands and landfills.
Challenging winter conditions are common at Pallas GAW station. Picture: Niku Kivekäs
Carbon dioxide, methane, and nitrous oxide are the most important greenhouse gases, whose atmospheric concentrations are increasing due to human activities. Accurate internationally calibrated concentration measurements are needed for monitoring their trends. Observations from global monitoring network, together with atmospheric transport models, are used to estimate large-scale sources and sinks. Global Atmospheric Watch programme of the World Meteorological Organization coordinates the global network and primary calibration scales. Integrated Carbon Observing System infrastructure coordinates the European regional network.
Finnish Meteorological Institute operates Pallas-Sodankylä GAW-station. In Pallas node, the main greenhouse gases are measured continuously and weekly air samples are sent to NOAA in Boulder, USA for analyses as part of the Cooperative air sampling network of the NOAA/ESRL. The regional ICOS network for accurate carbon dioxide and methane observations in Finland is expanding to have measurements at Puijo-tower in Kuopio, Sodankylä node of the GAW station and Utö island on the Baltic Sea. Refined greenhouse gas source and sink estimates for Finland are foreseen when data from these new stations have accumulated. FMI is cooperating with Russian Hydrometeorological Service to measure greenhouse gas concentrations at Tiksi on the coast of the Laptev Sea.
Service of Eddy-covariance tower at a wetland in Pallas. Picture: Timo Lindholm
The greenhouse gas exchange between atmosphere and biosphere varies markedly depending on the ecosystem and prevailing environmental conditions. CO2 is fixed to the ecosystem by the plant photosynthesis. On the other hand, CO2 is released to atmosphere by plant respiration and soil microbes. During the Holocene, the forests and wetlands of boreal zone have accumulated great carbon reservoirs in the peat and mineral soils. CH4 is formed when organic matter decomposes in anoxic condition. The natural CH4 formation is greatest in humid ecosystems (wetlands, lakes). Human activities release significant CH4 emissions from landfills and ruminants. N2O emissions are rather small from natural ecosystems but the agricultural soils are an important source for N2O due to the use of nitrogen fertilizers.
The GHG exchange between the atmosphere and ecosystems in about 10 ha scale can be measured by the eddy covariance method by observing gas concentrations and vertical wind speed by fast response instruments. From these observations it is possible to calculate the short term balance (30 min) and further the annual balance of different GHG.
Greenhouse Gases research group measures continuously CO2, H2O, sensible heat and momentum fluxes at several sites by the above described eddy covariance method. The CH4 flux is included at appropriate sites (wetlands, landfills). Additional gas components like H2 and N2O, are measured campaign wise using chambers techniques.
The group participates in Global and European flux measurement networks.
Carbon storage in mineral soils based on ECHAM5/JSBACH/YASSO-modelling. Figure: Tea Thum
Modeling in the Greenhouse Gas group consists of biogeochemical modeling of ecosystems and meteorological modeling of atmospheric processes and transport. The applied models include detailed soil and vegetation process descriptions as well as case specific parameterizations. The applications cover a wide range of spatial scales from local site studies to global simulations.
Modeling of regional and global balance of greenhouse gases in present and future climates is carried out in the framework of COSMOS model family. Work is also done in collaboration with other European and international modeling groups.
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