Estimating Arctic CH4 Emissions Using Top-Down …...(~ 0.1 to 1.2 TgCH 4 /yr) Slide-16 Arctic Flux...
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Arctic Flux & Crucial Workshop, Hyytiala, FN Estimating Arctic CH 4 Emissions Using Top-Down Approaches Lori M. Bruhwiler NOAA Earth System Research Laboratory Slide-1
Transcript of Estimating Arctic CH4 Emissions Using Top-Down …...(~ 0.1 to 1.2 TgCH 4 /yr) Slide-16 Arctic Flux...
Arctic Flux & Crucial Workshop, Hyytiala, FN
Estimating Arctic CH4 Emissions Using Top-Down Approaches
Lori M. BruhwilerNOAA Earth System Research Laboratory
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What is driving the recent growth?Anthropogenic?Natural?Is the Arctic Contributing?
The Global Scale Top-Down View:Net Emissions = d[CH4]/dt + [CH4]/τ
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Schaefer et al., 2016; Nisbet et al., 2016: Most of the recent increase is likely to be due to non-Arctic microbial sources, probably in the Tropics
Agriculture/Animals? Wetlands? Both?
S. Michel, INSTAAR
Global-Scale Source Attribution
E. Dlugokencky
Arctic Flux & Crucial Workshop, Hyytiala, FN
CH4 Growth Rate (ppb/yr)
Constraining the Spatial Distribution of Emissions
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Current Surface Network
Estimated Atmospheric State(Concentration and Emissions)
Satellites, TCCON(Column Data)
Remotely SensedEcological Data
Prior Emission Estimates
Getting to the Spatiotemporal Scales We Care About…
Earth SystemAnalyzer-CH4
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Arctic Flux & Crucial Workshop, Hyytiala, FN Page XX-6
Global Atmospheric Inversion Results
AMAP, 2015; Kirschke et al., 2012
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Source Tg CH4 yr-1
Wetlands � 15.5 (11.1-27.4)
Biomass Burning � 0.6 (0.4-1.0)
Anthropogenic � 9.3 (7.2-10.5)
Total Budget of Arctic CH4: 25 (18 – 29) TgCH4/yr
Bottom Up: 76 (50 – 133) TgCH4/yr
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Total Budget of Arctic CH4: 76 (50 – 133) TgCH4/yr
Process TgCH4/yr Reference
Arctic Tundra Wetlands 26 (15 to 68) McGuire et al.,2012
High Northern Lakes(Glacial/Post-Glacial, Thermokarst, Peatland Ponds, Beaver Ponds)
17 ( ±10) Vik et al., 2014, in press
“Anomalous Hydrates” in Laptev Sea Sediments
17 Shakhova et al., 2013
Cold Season Tundra Emissions 12 (±5) Zona et al., 2016
Autumn “Freeze-out” Emissions 4 Mastepanov et al., 2008
The “Bottom-Up” Approach
Arctic Flux & Crucial Workshop, Hyytiala, FN
Why Do Top-Down and Bottom-Up Approaches Disagree?
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• Transport Biases in Inversions
• Difficult to Use Continental Sites• Models may be Biased Towards
Stability
• Spatial biases in flux observations could exist.
• It’s difficult to scale process observations to the entire Arctic.
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Do Inversions Agree on IAV?
Are There Emission Trends ?
Estimated ArcticEmissions
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Are Arctic Emissions Changing and Can We Detect These Changes Using Top-Down Approaches?
AMAP, 2015
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Atmospheric CH4 Monitoring Sites
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AMAP, 2015
We Need Long Time Series to Detect Small Trends!
Arctic Flux & Crucial Workshop, Hyytiala, FN
Is There Evidence of Changing Arctic CH4 Emissions?(No)
• Sweeney et al., GRL, 2016: No evidence of changing emissions at Barrow, AK over 29 years.
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Arctic Flux & Crucial Workshop, Hyytiala, FN
What Signals Are Present at ”Background Sites”?
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Arctic Flux & Crucial Workshop, Hyytiala, FN
Is There Evidence of Changing Arctic CH4 Emissions?(Yes)
• Barlow et al., ACPD, 2016: The seasonal cycle of atmospheric CH4 is changing at Barrow, AK. Nearby wetland emissions may be increasing by ~0.5%/yr since 1986.
• Walter et al., Nature, 2016: 0.2-2.5 PgC may have been released from Arctic Lakes over the past 60 years as a result of permafrost thaw. (~ 0.1 to 1.2 TgCH4/yr)
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Final Comments
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It is hard to detect changes in Arctic Emissions (25 TgCH4/yrout of ~550 TgCH4/yr globally) given high atmospheric variability.
We need sustained observations of fluxes and atmospheric concentrations with adequate spatial coverage.
We need to understand the global CH4 budget, anthropogenic and natural.
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The Annual Greenhouse Gas Index (NOAA/GMD)
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The Permafrost Carbon Feedback
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1,330-1,580 PgC
5-15% of this could be vulnerable to release to the atmosphere as CO2 and CH4 during this century.
Release will be gradual and occur over multiple centuries.
(Schuur et al., Nature, 2015)
Arctic Flux & Crucial Workshop, Hyytiala, FN Slide-21The Carbon Brief
