Atmospheric methane concentrations and the link to warming arctic permafrost

Transcription

1 Atmospheric methane concentrations and the link to warming arctic permafrost Northern Manitoba, Natural Resources Canada Morgan Farley-Chrust April 8, 2010 U of U Atmospheric Science

2 Outline Why is Methane (CH₄) Important Atmospheric Methane Sources & Sinks Atmospheric Methane Levels Permafrost and Thermokarst formation Measurements of Global Methane Concentrations Conclusions

3 Methane Powerful greenhouse gas with 2 nd largest radiative forcing behind CO₂ currently Global warming potential (GWP) much larger than CO₂ GWP of 72 (20 year span) GWP 25 (100 year span) Source: 4 th Assessment report of the IPCC

4 Atmospheric Methane Sources Biogenic (~70% of total*) Peat / Wetlands Rice agriculture (A) Livestock (A) Landfills(A) Forests Oceans Non-Biogenic (~30% of total) Fossil fuels(a) Biomass burning(a) Waste treatment (A) Geological *4 th Assessment report of the IPCC

5 Methane Sinks Reaction with OH in the troposphere- dominant Stratospheric loss Uptake in soils Reaction with Cl in the marine boundary layer

6 Source: 4 th Assessment report of the IPCC

7 Historic Methane Concentration & Growth Source: 4 th Assessment report of the IPCC

8 Permafrost Distribution *Source: 4 th Assessment report of the IPCC

9 Permafrost Warming *Source: 4 th Assessment report of the IPCC

10 Thermokarst Development Occurs when the surface thaws and the ground subsides Creates pools and thaw lakes underlain by discontinuous permafrost Recent studies show that CH₄ emissions are highly sensitive to temperature and hydrology Evidence of complex ecosystem capable of adapting to change (Dise 2009) Thermokarst in Yakutsk, Russia

11 Results - CH₄ flux from thermokarst lakes in Siberia Previous estimates from N. wetlands of <6-40 Tg CH₄/year (which author cites does not include this region) Yielded a regional flux of 3.8 Tg CH₄ / year this represents % increase Measured a 14.7% increase in lake area using GIS resulted in a 58% increase in lake CH4 emissions, or 1.4 TgCH4/ yr between 1974 (2.4 TgCH4 yr)/ and 2000 (3.8 TgCH4 /yr) Concludes that N Siberian lakes are a larger source of atmospheric methane than previously recognized

12 Global CH₄ Measurements -NOAA Earth System Research Laboratory Goal: understand cause of increase starting in 07 Measurements from 46 global sites ( ) CH 4, C/ C( C), CO, SF Created evenly spaced matrix of CH₄ mole fraction Calculated global and zonal CH₄ averages (NH, SH, Tropical, Polar) 6 CH 13 C/ CO 4 12 Dlugokencky E.J. et al C( C) GMD Carbon Cycle Sampling Network, NOAA Earth System Research Laboratory (ESRL)

13 Results Global Global Ave CH₄ Concentration From 1996 to 2006 CH₄ remained nearly constant In 2007 levels increased 8.3 ±0.6 ppb Largest increase since 1990 s Global Ave CH₄ Growth Rate Polar N. Ave CH₄, CO residuals Largest zonally averaged increase in 2007 was at polar northern latitudes However increase was larger for SH average vs. NH average Tropics Ave CH₄, CO residuals Dlugokencky E.J. et al. 2009

14 Results Polar Northern Latitudes Global Ave CH₄ Concentration 97/98 & 02/03- anomalies in Boreal biomass burning are known to have occurred 07 -attributed to anomalously warm arctic temperatures Global Ave CH₄ Growth Rate Polar N. Ave CH₄, CO residuals Cite that growth rate returned to near zero in 2008 Concluded that since growth rate returned to zero, tipping point has not been reached in the arctic Tropics Ave CH₄, CO residuals Dlugokencky E.J. et al. 2009

15 Results Global Ave CH₄ Concentration Global Ave CH₄ Growth Rate Tropics biomass burning wide spread CO residuals low for period Above normal precipitation attributed to increases in CH₄ (La nina event) Polar N. Ave CH₄, CO residuals Tropics Ave CH₄, CO residuals Dlugokencky E.J. et al. 2009

16 Conclusions Understanding of the global methane budget is poor Difficult to attribute measured concentrations to individual sources and sinks due to large spatial dependence Evidence shows that CH₄ emissions from wetlands is sensitive to temperature and precipitation However, wetlands response to global climate change is poorly understood and more complex stabilization mechanisms could be at play

17 References A. Anthony Bloom,1 Paul I. Palmer,1* Annemarie Fraser,1 David S. Reay,1 Christian Frankenberg2 2010: Large-Scale Controls of Methanogenesis Inferred from Methane and Gravity Spaceborne Data, Science Vol 327 Denman, K.L., G. Brasseur, A. Chidthaisong, P. Ciais, P.M. Cox, R.E. Dickinson, D. Hauglustaine, C. Heinze, E. Holland, D. Jacob, U. Lohmann, S Ramachandran, P.L. da Silva Dias, S.C. Wofsy and X. Zhang, 2007: Couplings Between Changes in the Climate System and Biogeochemistry. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. E. J. Dlugokencky, L. Bruhwiler, J. W. C. White, L. K. Emmons, P. C. Novelli, S. A. Montzka, K. A. Masarie, P. M. Lang, A. M. Crotwell, J. B. Miller, and L. V. Gatti(2009), Observational constraints on recent increases in the atmospheric CH4 burden, Geophys. Res. Lett., 36, L18803, doi: /2009gl Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland, 2007: Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. K. M. Walter, S. A. Zimov, J. P. Chanton, D. Verbyla & F. S. Chapin III(2006) Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming NATURE, Vol 443, 7 September 2006 Kimberly P. Wickland, Robert G. Striegl, Jason C. Neff, and Torsten Sachs(2006) Effects of permafrost melting on CO2 and CH4 exchange of a poorlydrained black spruce lowland, JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, G02011, doi: /2005jg000099, 2006

18 Wickland et al. -Thermokarst region in Alaska

19 Wickland et al. - CH₄ flux and active layer depth CH₄ Flux Active Layer Depth