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Measurement of the Isotopes of Methane in the Arctic – from Micro to Macro Scale Dave Lowry 1, Rebecca Fisher 1, James France 1, Mathias Lanoisellé 1,

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Presentation on theme: "Measurement of the Isotopes of Methane in the Arctic – from Micro to Macro Scale Dave Lowry 1, Rebecca Fisher 1, James France 1, Mathias Lanoisellé 1,"— Presentation transcript:

1 Measurement of the Isotopes of Methane in the Arctic – from Micro to Macro Scale Dave Lowry 1, Rebecca Fisher 1, James France 1, Mathias Lanoisellé 1, Rebecca Brownlow 1, Euan Nisbet 1, Axel Wellpott 2, Stéphane Baugitte 2 1Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, UK 2Facility for Airborne Atmospheric Measurements (FAAM), Cranfield University, Cranfield, Bedford MK43 0AL, UK Presented at the: MOCA Kick-off Meeting, Oslo, 29 Oct 2013

2 Methane Isotope Measurements in and Above the Arctic Region Aims of this work 1)Improve characterisation of the boreal wetland methane isotopic source signature – does it vary by wetland type / location / season? 2)Measure the methane source signature above the European Arctic for different air masses to calculate the isotopic signature of air arriving from different regions 3)Which scale of measurement is best for regional and global modelling of methane emissions – micro or macro? This includes a range of scales and platforms: Long-term records for background monitoring stations in the Arctic Chamber studies in wetlands Diurnal sampling of air at low levels over wetlands Collection on mobile platforms – ships, cars and planes

3 Global CH 4 Sources –Isotopic Fingerprinting RHUL data unless stated. D data from Sowers (2006) Measurements made at source or within plumes coming from them Big errors on source signatures lead to even bigger errors when modelling the distribution of sources at regional or global scale

4 The Keeling Plot Method Plots δ 13 C vs 1/CH 4 conc. (Usually from samples within / near a source) Assumes added methane is all from the same source and background is constant y-intercept is effectively the point where added methane = infinite concentration y-intercept = methane source signature in terms of δ 13 C

5 Air samples are collected in 3 or 5L Tedlar bags using small battery operated pumps, allowing low cost air sampling. CH 4 mixing ratios are stable in the bags even if stored for several months. This provides enough air for triplicate CH 4 concentration measurements by Picarro G1301 CRDS and triplicate 13 C measurements by CF-GC-IRMS. Stainless steel or glass flasks are used for sites where CO 2, CO and H 2 measurements are also required Air Sampling for Methane Isotopic Measurements at Royal Holloway

6 Methane Sources in the Arctic Methane sourceReferenceδ 13 C () Wetland, N. FinlandSriskantharajah et al., to -66 Wetland, Hudson Bay Lowlands, CanadaKuhlmann et al., ± 3.2 Tundra, AlaskaQuay et al., to -55 Wetland, SiberiaSugawara et al., 1996 Kuhlmann et al., 1998 Meth MonitEUr, to ± Ebullition from thermokarst lakes, N. SiberiaWalter et al., to -58 Marine clathrate, Haakon Mosby mud volcano Milkov, 1998; Lein et al., 1999; Ginsburg et al., to -56 Marine clathrate, W. SpitsbergenFisher et al., to -46 Onshore hydrate, Mackenzie delta, CanadaLorenson et al., to Ob River gasfield emissionsMeth MonitEUr, to -48 Boreal forest fires, Ontario + NWT, CanadaRHUL, unpublished-28.5 ± 1.0 Wetland (N. Finland) -69 Summer 2008 Bulk Arctic signature -65 Gas field (Ob River, Russia) -49 Thermokarst lakes (Walter et al., 2006) -83 to -58 Pine forest fire (ON, Canada) -28 Hydrate (W. Spitsbergen slope) -51 Spring 2009 Bulk Arctic signature

7 Alert Arctic CH 4 13 C at Background Stations δ 13 C measured in flasks and bags collected at Alert, Zeppelin, Pallas Weekly bags now also collected at Sodankylä (50m on tower) ZeppelinPallas ALT ZEP PAL Late summer/autumn elevated CH 4 depleted in 13 C at Pallas. Source signature -72 – regional wetland sources

8 Isotopic Signature of Methane at Pallas Intercept of a geometric mean regression gives a methane isotopic source signature of -72 ± 2 Matches the wetland signature measured in the ground based and aircraft campaigns June-October (2011/2012) Pallas and Alert, 2009

9 Back Trajectory Analysis for Svalbard Area Sampling, 2008 (Fisher et al., 2011) CH 4 mixing ratio δ 13 C () 4 th – 8 th September highest methane mixing ratio: Air passed over Ob river area, NW Siberia. Keeling plot for these days gives δ 13 C source signature = -61 ± 3 (40% gas leak, 60% wetland?) Can miss sudden synoptic changes when sampling is weekly

10 Wetland Chamber Measurements, Sodankylä Methane collected in 17 chambers had an isotopic source signature ranging from -76 to -53 Emission rates in the chambers over wetland ranged from 0.2 to 11.6 mg CH 4 /m 2 /h (flux measurements by CEH Edinburgh) The isotope signatures and the chamber flux measurements can be used to calculate a flux weighted mean source signature: ± 2.9

11 Methane Isotopic Composition of Emissions from Lompolojänkkä Mire, Pallas, Finland (Sriskantharajah et al., 2012)

12 Keeling Plots to Determine Source Isotopic Signature of Wetland Emissions in Northern Scandinavia in July 2012 Sodankylä Kaamanen Faerdesmyra Lompolojänkkä -71.3

13 Is there a latitudinal gradient in the isotopic signature of CH 4 from wetlands in Lapland?

14 Spatial Variability of CH 4 and 13 C at High Latitudes - Ship and Road Trip Sampling Campaigns Cruises – JCR 253 (July-Sept 2011) – UK - Svalbard hydrate zone - UK – Catarina (June-July 2012) – Porto to Newfoundland via Greenland – JCR 269b (July 2012) – Reykjavik - Svalbard hydrate zone – Reykjavik – GEOMAR (Aug-Sept 2012) – Rejkjavik - Svalbard hydrate zone – Bremerhavn Road trips – July 21-22, 2012 – Kiruna – Sodankyla – Kaamanen – Kiruna – Sept 9-11, 2012 – Sodankyla – Kaamanen – Berlevag – Tana – Sodankyla – Aug 17-17, 2013 – Kiruna – Narvik – Alta – North Cape – Berlevag – Kaamanen – Sodankyla – Lulea - Kiruna

15 Summer 2011

16 JCR (July) and Geomar Cruises (Sept, 2012) Possible wetland input

17 Summer 2012 Norwegian coastal samples – July

18 July to Sept – 2011/12 Keeling Comparison 2011 JCR Svalbard – Scotland transect 2011 Zeppelin station daily sampling 2012 JCR + Geomar cruises – Iceland – Norwegian Sea - Svalbard Very similar source composition dominating excess methane in the high European Arctic for the summers of 2011 and 2012

19 July 2012 Road Trip Kjolnes Pallas

20 Lapland Road Trip (July 21-22, 2012) Moving with the airmass from NW to SE ppb increase in CH 4 associated with a 0.4 to 0.5 depletion in 13 C from the Norwegian coast 20 ppb enhancement next to wetland hotspots in Finland around Sodankyla Keeling plot for 1.5 days under the same weather system indicates that the source of this excess methane (-70 ) is wetland

21 Measurements and Sample Collection on the FAAM BAE-146 Research Aircraft The aircraft is equipped with Los Gatos FGGA (FAAM) and more recently an Aerodyne QCL (Univ. Manchester) for continuous measurement of atmospheric CH4 during the flights FAAM core chemistry instrumentation rack installed in mid-cabin FGGA Pump Calibration The response time from air inlet to data screen is currently 4 seconds for the FGGA and 1 second for the QCL

22 MAMM – Flight Campaigns Summer flying at 75 and 150m over wetlands in Finland and Sweden Use FGGA and QCL display to choose sample collection times Flights linked to ground-based sampling at chamber, wetland and road-trip scale

23 Finnish Wetlands From Above – Aug 2013

24 Low Level Flying Over Wetland Areas, August 2013: B797 Concentration range in WAS bottles: 1851 to 1961 ppb Highest concentration, lowest δ 13 C (1961 ppb, measured at points A and B) Source ± 0.7 (R 2 = 0.98) A B

25 August 2013 WAS Data (Flights B ) Combining all the flight data up to 1500m over Lapland this summer gives a single correlation suggesting that wetland is the only source for the methane increment during that campaign Compared with flight B720 (2012 wetland flight below 1500m) the source signature is the same but the error is much smaller in 2013 Source ± 0.4 (R 2 = 0.94, n = 155)

26 MEVALI Campaign (March 2012) - All Flights Wetlands frozen, so no wetland component in the CH 4 increment

27 Isotopic Signature of Methane Sources by Latitude S-SW winds N-NE winds Arctic Winter – dominated by gas leaks and heating All information gathered so far from our and North American wetland studies suggest that the signal coming from Canadian wetlands is -63 ± 3, but the signal from Scandinavian and Siberian wetlands is much lower, averaging -70 ±3. Different vegetation types in the mires might be important in this variation as the Abisko diurnal suggests. Are wetland emissions from Lapland becoming lighter? - 68 in 2008/9 to -71 in 2012/13. Check rainfall / wetland areas. Less oxidation. The only regional enriched source (-28 ) are forest fires and these are very sporadic in timing and rarely influence the isotopic signal in this region

28 Which Isotopic Measurement Scale Provides the Best Data for Regional and Global Modelling? Chambers sample emissions from very small areas which target different water table and vegetation types therefore the 13 C is too variable for large scale modelling Long-term fixed site records provide a good test of the performance of models, but not data for model input Flights provide the best spatial coverage and an averaged isotopic signature for the boundary layer, but are expensive and difficult to plan to fit with the best weather conditions for emissions Cruises are rarely close to the methane source regions unless hydrate unexpectedly destabilizes A combination of road trips and diurnal sampling at source provide good regional data coverage and confirmation of the contributors to the excess CH 4


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