Permafrost what is permafrost where does it occur what problems exist.
Representing permafrost affected ecosystems in the CLM · Representing permafrost affected...
Transcript of Representing permafrost affected ecosystems in the CLM · Representing permafrost affected...
Representing permafrost affected ecosystems in the CLM: An example of incorporating empirical ideas into the CLM
Hanna Lee Climate and Global Dynamics Division National Center for Atmospheric Research
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Knowledge from the field/lab Model development
Global estimation of permafrost C-climate feedback
Reducing uncertainty
Biogeochemical consequences
• 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 GBC
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- Permafrost C
Potential Arctic-climate feedback
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+ Positive feedback
Arctic warming
Permafrost thaw
CO2CH4
Global warming
CO2 uptake by Plant growth
Decomposition
Soil N
Potential Arctic-climate feedback - Negative feedback
CO2CH4
Arctic warming
Permafrost thaw
CO2 uptake by Plant growth
Decomposition
Soil N
Global warming
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Physical consequences
Changes in local hydrology: Aerobic vs. Anaerobic -> C cycling 6
- Thermokarst formation
Land surface subsidence created by ice rich permafrost thaw
Climate effects from permafrost C release
Deep permafrost C release under aerobic and anaerobic conditions : Faster C release under aerobic conditions
Modified from Lee et al. 2012 GCB 7
Aerobic Anaerobic
Laboratory incubation
Aerobic
Climate effects from permafrost C release
Modified from Lee et al. 2012 GCB 8
Deep permafrost C release under aerobic and anaerobic conditions : Comparable in atmospheric forcing with CH4 effect
Aerobic Anaerobic
Laboratory incubation
Anaerobic
Research Question 1.
• How does permafrost thaw influence ecosystem carbon balance under warmer world?
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Interior Alaska tundra site
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Denali National Park 2003 aerial photo
Natural gradient of
permafrost thaw and
thermokarst development
Osterkamp & Romanovsky 1999 PPP
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Interior Alaska tundra site
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
Deep permafrost T increase
Denali National Park 2003 aerial photo
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Aboveground carbon balance
Autochambers
CO2 uptake: GPP
CO2 release: Reco
Balance: NEE
Aboveground Net Ecosystem Exchange of carbon
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Over 3 years: Minimal ≈ neutral Moderate = sink ( GPP, Reco) Extensive = source ( GPP, Reco)
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.
Minimal Moderate Extensive
Ne
t E
co
sys
tem
Ex
ch
an
ge
(gC
m-2
)
-80
-60
-40
-20
0
20
40
C sink:
More uptake
C source:
More release
Balance between carbon uptake and release
Net Carbon Exchange Projections
Carbon neutral when thawing started
+
0 -
Year
NEE
1965 2099 2005
1950
sink
source
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Thawing started
Net Carbon Exchange Projections
Carbon uptake of ~25 g m-2 in the early stage of thawing
+
0 -
Year
NEE
1965 2099 2005
+25 g m-2
1950
sink
source
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Early stage C uptake
Net Carbon Exchange Projections
Carbon release of ~32 g m-2 in the later stage of thawing
+
0 -
Year
NEE
1965 2099 2005
-32 g m-2
1950
sink
source
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Later stage C release
Net Carbon Exchange Projections
Carbon loss by 2099: 4.4-6.0 kg m-2 (9.4-12.9%)
+
0 -
Year
NEE
1965 2099 2005
-52 to -69 g m-2
1950
sink
source
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Expected equilibrium
Permafrost Zone Soil C Gelisol Soil Order (3m) 818 Pg x 9.4-12.9% 77-106 Pg Permafrost C Loss (0.8-1.1 Pg/yr) Current Land Use Change (1.5±0.5 Pg/yr)
Permafrost Carbon Loss in global carbon context
Schuur, Vogel, Crummer, Lee, Sickman, Osterkamp 2009 Nature 459: 556-559. 18
Using the three sites as representatives of permafrost thaw…
Research Question 2.
• What is the climate feedback from permafrost C?
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Absorbed solar
Dif
fuse
so
lar
Do
wn
wel
ling
lon
gwav
e
Reflected solar Em
itte
d
lon
gwav
e
Sen
sib
le h
eat
flu
x
Late
nt
hea
t fl
ux
ua 0
Momentum flux Wind speed
Soil heat flux
Evaporation
Melt
Sublimation
Throughfall
Infiltration Surface runoff
Evaporation
Transpiration
Precipitation
Heterotrophic respiration
Photosynthesis
Autotrophic respiration
Litterfall
N uptake
Vegetation C/N
Root litter Soil C/N
N mineralization
Fire
Surface fluxes Hydrology
Biogeochemical cycles
SCF
Aerosol deposition
Bedrock
Soil (sand, clay, organic)
Unconfined aquifer Sub-surface
runoff
Aquifer recharge
Phenology
BVOCs
Water table
Soil
Dust
Saturated fraction
N dep N fixation
Denitrification N leaching
Glacier
Lake
River Routing
Runoff
River discharge
Urban
Land Use Change
Wood harvest
Vegetation Dynamics
Growth
Competition Wetland
Lawrence et al., Journal Advances Modeling Earth Systems, 2011
Disturbance
Improvements in Community Land Model 4.5
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Permafrost layer
Wetlands
CO2/CH4 dynamics
Transient layer that acts like permafrost
Physical consequences
Changes in local hydrology: Aerobic vs. Anaerobic -> C cycling 21
- Thermokarst formation
Land surface subsidence created by ice rich permafrost thaw
22 Agriculture & Agri-Food Canada
Excess ice and permafrost parameterization
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Control
Soil layers and Excess ice
Control: Regular CLM soil layers
Used ground ice data from NSIDC
Excess ice
Ice and soil
mixture at
layers 8-10
Melting
Surface
subsidence
Excess ice and permafrost parameterization
High: > 20%
Medium: 10-20%
Low: 0-10%
Brown, J., O.J. Ferrians, Jr., J.A. Heginbottom, and E.S. Melnikov.. 2002. Circum-Arctic Map of Permafrost and
Ground-Ice Conditions. Version 2. [indicate subset used]. Boulder, Colorado USA: National Snow and Ice Data Center.
Continuous: 90-100%
Discontinuous: 50-90%
Sporadic: 10-50%
Isolated: 0-10%
Soil temperature patterns: Annual variability
25 • Soil warming slowed ~1°C by the end of the century
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Soil moisture patterns
Soil moisture increases
Soil water storage increases
Most of excess ice melt water goes to soil water storage
Surface subsidence simulations (Recent/RCP8.5)
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• Land surface subsidence as a function of excess ice melting
• Grid cell mean
Improved model and climate feedback
Arctic warming
Permafrost thaw Expanded wetlands
Lakes drain, soils dry CO2
CH4
Global warming
CO2 uptake by Plant growth
Decomposition
Soil N
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Enhanced predictions of Arctic-climate feedback with improved models