Arctic ecosystems as key biomes in climate-carbon feedback Hanna Lee Climate and Global Dynamics Division National Center for Atmospheric Research
Outline Permafrost carbon Permafrost carbon-climate feedback cycles Thermokarst influence on permafrost carbon feedback cycles Using CLM to better represent permafrost processes 2
Warming in the Arctic Northern Hemisphere: 0.4ºC increase in the past two decades IPCC (2007) Arctic: 1.2ºC increase in the past two decades ACIA (2004)
Biogeochemical consequences - Permafrost C Permafrost 1672Pg Carbon stored in permafrost 1/2 of global soil C stock x 2 more than C in the atmosphere Thawed permafrost will release C-based greenhouse gases at a faster rate! Schuur et al. 2008 BioScience Tarnocai et al. 2009 GlobalBiogeochemCyc 4
Why permafrost carbon? Permafrost carbon (1600) adapted from U.S. DOE, Biological and Environmental Research Information System 5
Vulnerability of permafrost C Permafrost Zone Soil C Gelisol Soil Order (3m) Permafrost C Loss Current Land Use Change 818 Pg x 9.4-12.9% 77-106 Pg (0.8-1.1 Pg/yr) (1.5±0.5 Pg/yr) Schuur et al. 2009 Nature 459: 556-559. 6
Potential Arctic-climate feedback Global warming + Positive feedback Arctic warming CO 2 uptake by Plant growth Permafrost thaw Soil N Decomposition CO 2 CH 4 7
Arctic shrub growth and tree line expansion 1949 2001 Photo from the Chandler River located at 68 25.14' N, 161 15.24' W: 7/4/1948 and 7/29/2001. (Tape et al., 2006). 8
Potential Arctic-climate feedback - Negative feedback CO 2 uptake by Plant growth Global warming Arctic warming Permafrost thaw CO 2 CH 4 9
The effects of N fertilization on shrub growth Toolik lake Long-Term Ecological Research site N fertilization over 20 years Warming & thawing permafrost stimulated decomposition and release N back to very N limited ecosystem 10
Potential Arctic-climate feedback - Negative feedback CO 2 uptake by Plant growth Global warming Arctic warming CO 2 CH 4 Permafrost thaw Soil N Decomposition 11
Physical consequences - Thermokarst formation Land surface subsidence created by permafrost thaw Changes in local hydrology: Aerobic vs. Anaerobic -> C cycling 12
Aerobic/Anaerobic influence on permafrost carbon and climate feedback Atmospheric feedback CO 2 > CO 2 /CH 4 > CO 2 /CH 4 Faster decomposition Aerobic Aerobic Anaerobic Anaerobic Warming Permafrost carbon 13
Aerobic/Anaerobic influence on permafrost carbon and climate feedback Atmospheric feedback CO 2 < CO 2 /CH 4 << CO 2 /CH 4 Greater GWP Aerobic Aerobic Anaerobic Anaerobic Warming Permafrost carbon 14
Climate effects from permafrost C release Laboratory incubation Aerobic Anaerobic Deep permafrost C release under aerobic and anaerobic conditions : Faster C release under aerobic conditions Modified from Lee et al. 2012 GCB 15
Climate effects from permafrost C release Laboratory incubation Aerobic Anaerobic Deep permafrost C release under aerobic and anaerobic conditions : Comparable in atmospheric forcing with CH 4 effect Modified from Lee et al. 2012 GCB 16
Research Questions How does permafrost thaw influence ecosystem carbon balance under warmer world? What is the climate feedback from permafrost C? 17
Research Question 1. How does permafrost thaw influence ecosystem carbon balance under warmer world? 18
Interior Alaska tundra site Denali National Park 2003 aerial photo 19
Interior Alaska tundra site Deep permafrost T increase Natural gradient of permafrost thaw and thermokarst development Osterkamp & Romanovsky 1999 PPP Three sites: Minimal Thaw: Typical tussock tundra before thawing Moderate Thaw: 15-20 yrs of permafrost thaw Extensive Thaw: over 50 yrs of thaw and deep thermokarst Denali National Park 2003 aerial photo 20
Ecosystem carbon cycling Photosynthesis Plant respiration GPP: photosynthetic uptake Reco: respiratory release NEE: GPP - Reco Litter Plant root respiration Microbial respiration CO 2 Soil Organic Matter
Aboveground carbon balance CO 2 uptake: GPP Autochambers Balance: NEE CO 2 release: R eco Temporally explicit measurements 22
Belowground permafrost carbon release Aboveground CO 2 flux measurement Soil Flux Chambers CO 2 Soil Gas Wells CO 2 Chambers: Photosynthetic uptake Plant respiration Permafrost carbon release CO 2 CO 2 CO 2-10cm -20cm -30cm Gas wells: Root respiration Permafrost carbon release CO 2-40cm Belowground CO 2 measurement 23
Aboveground Net Ecosystem Exchange of carbon Balance between carbon uptake and release Net Ecosystem Exchange (gc m -2 ) 40 20 0-20 -40-60 -80 C sink: More uptake C source: More release Minimal Moderate Extensive Over 3 years: Minimal neutral Moderate = sink ( GPP, R eco ) Extensive = source ( GPP, R eco ) Modified from Schuur, Vogel, Crummer, Lee, Sickman, Osterkamp 2009 Nature 459: 556-559. Vogel, Schuur, Trucco, Lee 2009 J Geophys Res 114, G4, doi:10.1029/2008jg000901. 24
Belowground permafrost carbon release More CO 2 release in Extensive thaw Minimal Thaw Moderate Thaw Extensive Thaw Permafrost C release greater with more permafrost thawing Lee et al. 2010 JGR
150 100 50 0-50 -100-150 -200-250 -300 14 C ( ) Depth (cm) Respiration Partitioning using 14 C 14 CO 2 14 CO 2 14 CO 2 14 CO 2 1000 800 600 Atmosphere 0 10 20 30 Minimal Thaw Moderate Thaw Extensive Thaw 400 40 200 50 60 0 70-200 1950 1960 1970 1980 1990 2000 80 Young 14 C ( ) Old Bomb signature Natural decay Organic matter deposit 26
14 C ( ) 150 100 50 0-50 -100-150 -200-250 -300 14 C ( ) Depth (cm) Respiration Partitioning using 14 C 14 CO 2 14 CO 2 14 CO 2 14 CO 2 1000 800 600 Atmosphere 0 10 20 30 Minimal Thaw Moderate Thaw Extensive Thaw 400 40 200 50 60 0 70-200 1950 1960 1970 1980 1990 2000 80 Young 300 14 C ( ) Old 200 Bomb signature 100 Natural decay 0 Organic matter deposit -100-200 -300 Recent detritus Plant respiration Old soil C 27
Ecosystem Respiration (g C m -2 yr -1 ) More old carbon loss with permafrost thaw 500 450 400 Minimal Thaw Moderate Thaw Extensive Thaw 350 300 250 R 2 =0.92 200 5 10 15 20 Old Carbon Loss (%) Contribution of permafrost C in total ecosystem C release greater with more thawing. Schuur, Vogel, Crummer, Lee, Sickman, Osterkamp 2009 Nature 459: 556-559. 28
Surface patterns under thawing permafrost Land surface before thawing 29
Surface patterns under thawing permafrost Relative subsidence up to 1.2 m Dryer/Colder Wetter/Warmer Land surface subsidence with thawing Wetter and warmer 30
Surface patterns under thawing permafrost Relative subsidence up to 1.2 m Dryer/Colder Wetter/Warmer Land surface subsidence with thawing More CO 2 Lee et al. 2010 JGR Wetter and warmer More subsided Relative subsidence 31
How can we model ecosystem C dynamics with thermokarst? Sampling Spatially explicit measurements Land surface patterns Ecosystem C balance Vegetation Soil environment 5m apart 50 pts each site Extensive Thaw 50m 32
UTMy How can we model ecosystem C dynamics with thermokarst? Lee et al. 2011 GCB Land surface patterns 7085249 7085232 7085215 Minimal Thaw 1.0000 0.5625 0.1250-0.3125-0.7500-1.1875-1.6250-2.0625-2.5000 Low relief land surface pattern Variability in surface patterns 7085198 389755 389768 389780 389793 389805 7085474 Moderate Thaw 7085456 7085438 389108 389128 389148 389168 7085626 1.000 0.563 0.125-0.313-0.750-1.188-1.625-2.063-2.500 7085611 Extensive Thaw 1.000 0.563 0.125-0.313-0.750-1.188-1.625-2.063-2.500 7085597 7085582 7085567 388943 388964 388984 389005 UTMx 1.000 0.563 0.125-0.313-0.750-1.188-1.625-2.063-2.500 High relief land surface pattern 33
78 How can we model ecosystem C dynamics with Carbon release Carbon uptake thermokarst? UTMy Annual Reco Annual GPP 7085253 7085253 Lee et al. 2011 GCB 7085233 Land surface patterns 7085249 389557 389574 389592 UTMy 7085232 1.0000 0.1250-0.3125-0.7500-1.1875-1.6250 7085441-2.0625-2.5000 7085215 389233 389793 389805 469-450 405-492 341-534 278 214-619 150 389539 7085453 7085597 389252 7085441 389270 7085198 389780 533-407 389557 389574 389592 7085466 70854530.5625 389768 596-365 Minimal Thaw 7085466 Minimal Thaw 389755 660-322 -577 7085233 389539-280 660-321 596-363 533-404 469-445 405-486 341-528 278-569 214-610 150 389233 389289 389252 389270 389289 Moderate Thaw Moderate Thaw 7085597 7085597 7085474-280 -280-321 -363 7085456-404 -445-486 7085438 389108-528 389128 389148 389168 7085626 660 1.000 0.563 0.125-0.313-0.750-1.188 7085583-1.625-2.063-2.500 7085583 7085611 388943 533-321 469-363 405-445 341-486 278-569 -528-610 -569 214-610 150 389162 389212-280 -404 Extensive 7085569 Thaw 1.000 389195 0.563 0.125 7085597-0.313-0.750-1.188 7085582-1.625-2.063-2.500 7085567 596 7085583 1.000 0.563 0.125-0.313-0.750-1.188-1.625-2.063-2.500 UTMx 7085569 7085569 389178 389195 389162 389212 389178 Extensive 389162 Thaw389195 389178 389195 389212 389212 Land surface patterns explain ecosystem carbon balance in the landscape! 388964 388984 389005 UTMx 34
Insights from Observations Permafrost thaw increase C uptake, but increase C release at a greater rate over time Land surface subsidence (thermokarst) can be used as a proxy for understanding ecosystem C balance on a landscape scale 35
Potential Arctic-climate feedback - Negative feedback Early stage of thawing CO 2 uptake by Plant growth Global warming Arctic warming Expanded wetlands CO 2 CH 4 Lakes drain, soils dry Permafrost thaw Soil N Decomposition 36
Potential Arctic-climate feedback Later stage of thawing Global warming + Positive feedback Arctic warming CO 2 uptake by Plant growth Expanded wetlands Permafrost thaw Soil N CH 4 Decomposition CO 2 Lakes drain, soils dry 37
Permafrost Carbon Loss in global carbon context Using the three sites as representatives of permafrost thaw Permafrost Zone Soil C Gelisol Soil Order (3m) Permafrost C Loss Current Land Use Change 818 Pg x 9.4-12.9% 77-106 Pg (0.8-1.1 Pg/yr) (1.5±0.5 Pg/yr) Schuur, Vogel, Crummer, Lee, Sickman, Osterkamp 2009 Nature 459: 556-559. 38
Research Question 2. What is the climate feedback from permafrost C? 39
Using Earth System Models Community Earth System Model, NCAR 40
Near surface permafrost extent Lawrence and Slater 2005 Lawrence, Slater, Swenson 2012 41
Conceptual diagram of Community Land Model 4.0 Diffuse solar Emitted longwave Downwelling longwave Latent heat flux Sensible heat flux Reflected solar Absorbed solar Aerosol deposition SCF Soil (sand, clay, organic) Bedrock Surface fluxes Soil heat flux Precipitation Momentum flux Wind speed 0 u a Evaporation Dust Sublimation Melt Soil Aquifer recharge Unconfined aquifer Transpiration Throughfall Water table Hydrology Evaporation Infiltration Saturated fraction Sub-surface runoff Surface runoff Phenology Fire Biogeochemical cycles Photosynthesis Soil C/N Vegetation C/N Litterfall N mineralization BVOCs Heterotrophic respiration Root litter N uptake Autotrophic respiration N dep N fixation Denitrification N leaching Glacier Lake Urban Wetland River discharge Wood harvest Runoff River Routing Land Use Change Competition Vegetation Dynamics Disturbance Growth Lawrence et al., Journal Advances Modeling Earth Systems, 2011 42
Observations Model 43
Improvements in Community Land Model 4.5 Diffuse solar Emitted longwave Downwelling longwave Latent heat flux Sensible heat flux Reflected solar Absorbed solar Aerosol deposition SCF Soil (sand, clay, organic) Bedrock Surface fluxes Soil heat flux Precipitation Momentum flux Wind speed 0 u a Evaporation Dust Transient layer that acts like permafrost Sublimation Melt Soil Aquifer recharge Unconfined aquifer Hydrology Transpiration Throughfall Water table Evaporation Infiltration Surface runoff Wetlands Permafrost layer Saturated fraction Sub-surface runoff Phenology Fire Biogeochemical cycles Photosynthesis CO BVOCs 2 /CH 4 dynamics Soil C/N Vegetation C/N Litterfall N mineralization Heterotrophic respiration Root litter N uptake Autotrophic respiration N dep N fixation Denitrification N leaching Glacier Lake Urban Wetland River discharge Wood harvest Runoff River Routing Land Use Change Competition Vegetation Dynamics Disturbance Growth Lawrence et al., Journal Advances Modeling Earth Systems, 2011 44
Excess ice and thermokarst parameterization Ice wedges in permafrost soil Problem in CLM Agriculture & Agri-Food Canada Anaerobic environment CO 2 /CH 4 emissions Exposed permafrost CO 2 emissions Government of Yukon Thermokarst development
Excess ice and permafrost parameterization Soil layers and Excess ice Control Excess ice Melting Surface subsidence CLM4.5 Ice and soil mixture at layers 8-10 Control: Regular CLM soil layers 46
Thermokarst predictions under future climate projections 2010 2050 2100 Unit: meter Lee et al. in prep Env Res Lett 47
Improved model and climate feedback Global warming Arctic warming CO 2 uptake by Plant growth Expanded wetlands Permafrost thaw Soil N CH 4 Decomposition CO 2 Lakes drain, soils dry Enhanced predictions of Arctic-climate feedback with improved models 48
Conclusions Permafrost C important and underestimated source of C in terrestrial-climate feedback Thermokarst development can influence the rate and types of C release Models are improving to better represent permafrost processes under changing climate 49