Increasing Wetland Emissions of Methane From A Warmer Artic: Do we See it Yet?

Lori Bruhwiler and Ed Dlugokencky

Earth System Research LaboratoryBoulder, Colorado

Arctic Climate Change Accelerating T increase since early-1990s

(>0.3°C decade-1) resulting in warming of wetland soils.

Decreasing snow cover and sea ice. Increased plant growth; northward

migration of tree line. Increased terrestrial precipitation. Destabilization of permafrost.

Permafrost Accelerating melting thermokarst

formation Expanding wetland area. Longer active season. Increased transport DOC to Arctic Ocean. Changing vegetation affects RF. Soils contain 500 to 900 Pg C, implying a

potential for huge CH4 and CO2 emissions.

Impacts on Infrastructure

Thermokarst Formation Thermokarst (thaw) lakes migrate naturally

and can be accelerated by climate change.

• Year-round flux measurements.

• Remote sensing, aerial surveys quantify emissions.

• 95% emissions from ebullition.

• 3.8 TgCH4 yr-1 from Siberian thermokarst lakes

• Increased by 58%, from 1974 to 2000.

• Carbon source, 35-43k years old, d13C~-70‰.

Walter et al., Nature, Sept. 2006

Methane Bubbling From Siberian Lakes

Simulation of Increased Wetland Emissions from Permafrost Destabilization

• Model: TM5- 6x4 Horizontal Resolution, 25 Levels

• Constant Sources/ Soil Sink optimized against observations from 2002 (e.g Bergamaschi,2005)

• Constant Photochemical Sink with OH optimized against MC observations (courtesy of P. Bergamaschi)

• HNH Wetlands - Perturbation Calculated Assuming Q10 Temperature Relationship and Observed Temperature Trends for High Northern Latitudes. Plus projected increases in coal, rice, oil and gas.

Optimized 2001 Emissions 525.63 TgCH4/yr (Courtesy of P. Bergamaschi)Coal 30,72 (TgCH4/yr)Oil/Gas 50.86 Enteric Fermentation/Manure 100.46Rice 59.74Biomass Burning 32.30Waste 73.62Wetlands 174.49 Wild Animals 5.00Termites 19.23Soil -37.79Oceans 17.00

Wetland Warming

CH4 emissions are very T sensitive.

• ET = ET0Q10(T-T0/10) where Q10 = ET+10/ET

• Q10 = 2-15 for CH4 wetland emissions. Mid-value used for this study.

Estimated Emission GrowthSources: IRRI, EIA Coal 31 TgCH4/yr 2%/yr

404.2%/yr China2.7 %/yr India

Oil/Gas 51 0.4%/yr NA 662.4%/yr Russia 4.0%/yr SH/Mid-East

Rice 60 0.75%/yr 127Wetlands 45 136(>60N)

Simulated Time Series: Perturbation-Control

Simulated Time Series:

Simulated Time Series:Projected Emission Changes

Detection Changes in CH4 Growth Rate.

Changes in Amplitude or Phase Shifts in the Seasonal Cycle

Changes in Spatial Gradients

How Useful Are Satellite Column Averages?

Global Growth Rate

No significant Change in Growth Rate.

Compensation among emissions changes?

Methane could be approaching steady state (Dlugokencky et al., GRL, 2003)

Picture the same for Polar Latitude Zone

Simulated Growth Rate

Increasing Emissions fromNorthern WetlandsShould Cause IncreasesIn the Global Growth Rate

The Annual Cycle Amplitude and Phase

Spatial Gradients- The Interpolar Difference

Dlugokencky et al., GRL 2003

Simulated Inter-polar DifferenceThe IPD will bea sensitive indicatorof increased emissions fromHigh Northern Latitudes

Enhance Detection and Attribution

Add Arctic in situ measurement sites Cherskii, NE Science Research Station (Siberia) Tiksi (Siberia), Toolik Lake (Alaska), Eureka (Canada) Yukon Basin (Alaska,USGS)

Develop robust analytical system LGR optical CH4 analyzer

Assimilation and Estimation of CH4 fluxes using Ensemble Kalman Filter Method with TM5

Regression Analysis suggests that current network won’t be able to differentiate emission changes from various sources.

Conclusions• There is currently no evidence from the

Cooperative Air Sampling Network of an increase in emissions from the Arctic

• Several sensitive diagnostics may be used to detect Permafrost Destabilization in the Arctic

Permafrost

*Regions (dry or wet) below 0°C for two consecutive years.

*On land

*Undersea