Methane measurements in Sodankylä 1. Introduction and Background Methane from Arctic wetland is closely implicated in rapid past global change. With Arctic mean annual temperatures currently rising two times faster than the global average temperature, and an extending growing season, quantification of methane emission from northern wetlands is important (Dlugokencky et al., in press). In 2007, after a long period of nearstability, global annual methane levels rose suddenly[3,4,5]. Part of the rise may have occurred in the Arctic [3,5] particularly in summer 2007 which brought spectacular sea ice retreat and an intense heatwave in the Siberian Arctic. Arctic methane comes from several distinct sources: wetlands, industrial gas leaks, decaying land and submarine methane clathrates, thermokarsts and fires (especially peat fires). Most sources of Arctic methane emission are highly dependent on temperature, with an Arrhenius-like dependence[15,16], but with different response timescales. Arctic wetland is active between the spring thaw and the freeze in autumn, and this is the time when methane fluxes to air are highest[17,18,19]. Bloom et al.13] and Ringeval et al. recently analyzed new atmospheric methane data and concluded that, although the global seasonal cycle is dominated by the tropical wetlands, the emissions from northern latitudes dominated the inter-annual variability. Overall understanding of the Arctic methane budget is poor. A key factor is that many emissions may be episodic, and may be missed by relatively infrequent field campaigns. The existing quasicontinuous Arctic CH4 measurement network is not dense enough for reliable estimates of CH4 emissions and differentiation of its sources. Measuring isotopes is vital, as the contribution to the Arctic CH4 budget of different sources, which could be distinguished by their isotopic signatures, might change relatively quickly. Currently, isotopic constraints remain weak because of the lack of data. There is an urgent need to complement the rather sporadic collection of GHG data, including flux and isotope measurements with a multi-measurement approach to establish first-order features of the strength, seasonality and functionality of GHG fluxes. Center for Ecology and Hydrology (CEH), Edinburgh, UK and Royal Holloway University of London (RHUL), Egham, UK are in the core of these studies with their established and ongoing flux and isotopic measurement programmes that would be complemented with the proposed studies in Sodankylä. 2. Objectives We propose the following measurement studies: Determination of mixing ratios and wetland fluxes of methane and other greenhouse gases as well as diurnal sampling for δ13CCH4 in Sodankylä, using in situ and flask-based measurements. This will link with high resolution measurement of greenhouse gases and flask collection forδ13CCH4 on the BAe146 research aircraft as it flies over the European Arctic and the wetlands as part of a NERC-UK project. The measurement campaigns are in accordance with InGOS objectives and the requested infrastructure is suitable for the work owing to its location above the Arctic circle and facilities including a wetland eddy flux measurement site and atmospheric surface and column (FTIR) concentration measurement sites. 2. Methods and Materials 2.1 Flux measurements Although the Arctic and subarctic regions are a large source of greenhouse gases, with potential for rapid change, relatively few measurements have been made and only in those parts of the Arctic that are relatively easily accessible. Our knowledge is based on measurements using small chambers, eddy covariance and atmospheric isotopic ratios. Chambers are very useful in identifying spatial heterogeneity within an ecosystem and understanding underlying processes, for example the relationship between CH4 flux and substrate availability or the importance of vegetation in transport of CH4 from soil to the atmosphere. The development of fast response high resolution lasers have made it possible to measure CH4 fluxes by eddy covariance and provide integrated fluxes at the field scale. In the Arctic the few eddy covariance CH4 measurements have identified seasonal temperature changes and the presence of senescent vegetation as importance drivers of the flux[32,33,34]. In spite of this understanding, not enough data are available to extrapolate accurately to the landscape and regional scales or to predict future trends. Field scale measurements of CH4 and CO2 fluxes will be made by eddy covariance using fast response, high resolution analysers (Los Gatos at Sodankylä run by FMI) and sonic anemometers for vertical wind speed measurements. The flux is calculated as the covariance between concentration and wind speed[32,41]. CEH will use static chambers, placed strategically to cover the heterogeneity of the Arctic study sites, to investigate spatial variability and processes controlling CH4, N2O and soil respiration fluxes. Samples will be collected into vials, and shipped to CEH for analysis of CH4, CO2 and N2O by gas chromatography. Fluxes are calculated from the increase in concentration inside the enclosed chamber with time. In addition CEH will record spatial and temporal changes in water table and together with FMI carry out a vegetation survey in the footprint areas of the new eddy covariance tower on this wetland. 2.2 Isotopic measurements Measurement of δ13C in CH4 in ambient air is the most powerful technique available to identify and quantify bulk Arctic CH4 sources since there is strong isotopic contrast between sources, with biological emissions being relatively rich in 12C, while geological and fire sources are typically depleted in 12C (i.e. isotopically 'lighter'). High precision measurements with small-sample isotopic techniques permit diurnal studies of CH4 isotopic composition of wetlands with “Keeling-plot” experiments. In contrast to chamber studies, such an approach allows estimation of the bulk isotopic signature of undisturbed emissions. Studies in Finland showed a tight δ13CCH4 range from -69 to -66 ‰. Thermokarst methanogenesis from point sources has variable isotopic composition (δ13CCH4 from -58 to -83‰ in Walter et al.). These sources can be distinguished from West Siberian natural gas at -50 ‰. Air samples measured at Royal Holloway, University of London (RHUL) collected during Canadian boreal forest fires showed δ13CCH4 of -29 to -27‰. High precision, automated stable isotopic analysis of atmospheric methane and carbon dioxide will be carried out using the method of Fisher et al.. Samples (3L) will be collected on intensive diurnal timescale at the Sodankylä wetland field site, in tedlar bags, for subsequent analysis at RHUL. Samples are analysed in the RHUL lab by a high precision continuous flow isotope ratio mass spectrometric technique, using 75 mL volumes of ambient air. The average precision of ±0.04 ‰ is high enough to provide accurate isotopic characteristics from source studies for input to isotope models. The method is rapid, allowing high numbers of samples to be analysed. The above mentioned flux and isotopic measurements are related to the FAAM aircraft measurement programme. Airborne and ground based measurement of GHG will be compared during the campaign in order to understand and constrain the uncertainty of up scaling, and to calibrate the aircraft concentrations against ground based flux and concentration measurements. The FAAM BAE 146 research aircraft will fly over the Sodankylä surface study area upwind, downwind and in vertical transects during July and measure CH4, N2O, CO2 concentrations and fluxes whilst ground measurements are made. Sample modules will allow automated flask filling for subsequent isotopic analysis. 3. Implementation Visiting scientists involved in July 2012 campaign: Ute Skiba (CEH) Julia Drewer (CEH) Kerry Dinsmore (CEH) Rebecca Fisher (RHUL) James France (RHUL) Dave Lowry (RHUL) FMI scientists involved in July 2012 campaign: Annalea Lohila (FMI) Tuomas Laurila (FMI) Tuula Aalto (FMI) Petteri Ahonen (FMI) Esko Kyrö (FMI) Timetable, July 2012 campaign: Participant Present in From Sodankylä CEH July 9 – July 14 Number of days 6 CEH July 9 – July 25 17 CEH July 19 – August 4 17 RHUL RHUL RHUL July 16 - July 25 July 23 - July 27 July 21 10 5 1 description Chamber measurements Chamber measurements Chamber measurements Isotope sampling Isotope sampling Isotope sampling Sodankylä measurement station is a large facility, and during the campaign there will always be FMI personnel present. Budget as requested from InGos, July 2012 campaign: TNA2 Number of Unit cost Total access calendar access days FMI 26 days 446,74 €/day 11 615,24 € Sodankylä site Travel CEH RHUL Subsistence CEH RHUL Total Number of travellers 3 2 Number of person working days 40 16 Flat rate Total 750 €/person 750 €/person Flat rate 2250 € 1 500 € 50 €/person/day 2 000 € 50 €/person/day 800 € 6550€ Grand total TNA2 access + Travel & subsistence: 4. Expected results 18 165 € Flux measurements will lead to new,improved understanding of the dependence of surface fluxes on relevant parameters (temperature, radiation, ground water, vegetation etc). Isotopic measurements will allow better characterisation of the Arctic wetland source in models. These crucial datasets, particularly in the Arctic, are currently few and sporadic. Data collected in a series of aircraft survey flights will significantly expand the new datasets, provide important complementary measurements for satellite instruments and, along with modelling, will allow the ground-based data to be put into regional and hemispheric context. We will determine if changes in the Arctic are resulting in increased CH4 emissions by combining our data with CH4 data from the small number of other Arctic stations. The results from these studies will be published in peer reviewed journals and utilized in university education. The data gathered will be made available for other researchers and general public. 5. Key literature 1. Nisbet E.G. & Chappellaz, J., Shifting gear, quickly. Science 324, 477-478, 2009. 2. Forster, P., V. Ramaswamy, P. Artaxo, et al., Changes in Atmospheric Constituents and in Radiative Forcing.,in Climate Change 2007: The Physical Science Basis. 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