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

2

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

3

- Permafrost C

Potential Arctic-climate feedback

4

+ 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

5

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?

9

Interior Alaska tundra site

10

Denali National Park 2003 aerial photo

Natural gradient of

permafrost thaw and

thermokarst development

Osterkamp & Romanovsky 1999 PPP

11

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

13

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

14

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

15

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

16

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

17

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?

19

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

20

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

23

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

26

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

28

Enhanced predictions of Arctic-climate feedback with improved models