When is the Permafrost Carbon Tipping Point?

When is the Permafrost Carbon Tipping Point?

National Snow and Ice Data Center, University of Colorado

Tingjun Zhang

Kevin Schaefer

Tim Schaefer

Lin LiuMe

Alessio Gusmereli

Permafrost Primer

Skiklomanov [2007]

Permafrost: Ground at or below 0°C for at least 2 consecutive years

Active Layer: A layer over permafrost that freezes and thaws annually

Permafrost Degradation: A decrease in permafrost extent; an increase in active layer thickness.

Permafrost Classification

Permafrost Classification by AreaPermafrost Classification by AreaContinuous (>90% of area)Discontinuous (50-90% of area)Sporadic (10-50% of area)Isolated (<10% of area)

Brown et al., 1998; Zhang et al., 1999

Permafrost Distribution by Country

Permafrost ProfilePermafrost Profile

Active Layer

Vegetation

Permafrost

Permafrost Profile

Exposed permafrost by river, Siberia [Davis, 2000]

Thermokarst, Alaska

CryoturbationCryoturbation• Movement of soil or rock due to Movement of soil or rock due to

repeated freezing and thawingrepeated freezing and thawing

Vegetation

Active Layer

Permafrost

Pleistocene Cryoturbation, France

Permafrost FeaturesPermafrost Features

Frost Heave, Yamal Stone Circles, Svalbard

Stone Circles, NW Territories Stripes, Glacier NP

Ice Wedges and PolygonsIce Wedges and Polygons

Polygons, Yena Polygons, Prudhoe Bay [Zhang, 2009]

Active Layer

Permafrost

Frozen

100th Winter

Frozen

1st Winter

Soil contracts & cracks

Thawed

1st Spring

Crack fills with water & freezes

Thawed

100th Spring

Ice Wedge

Ice Lenses and LayersIce Lenses and Layers

Active Layer

Permafrost

Year 1

Capillary suction of water to permafrost

Water freezes & expands

Year 1,000

Ice LayerIce Lens

Active Layer

Permafrost

Ice Lenses

Permafrost is Like ConcretePermafrost is Like Concrete

WicklandSchaefer

ThermokarstThermokarst

Slope Mountain, Alaska [Schaefer, 2012]

• Thermokarst: subsidence or collapse of ground surface due to melting of ground ice

Impacts of DegradationImpacts of DegradationFoundation Settling in Chersky

Qinghai-Xizang Highway Bridge

Alaska Road Heaves

Thermokarst in Yakutsk [Skiklomanov, 2005]

Impacts of DegradationImpacts of Degradation

Drying lake, Tibet [Zhang, 2007]

Rockfall, Matterhorn [Gruber, 2003] Ice-wedge thaw, Alaska [Davis, 2000]

Coastal Erosion, Alaska

Global Carbon CycleGlobal Carbon Cycle

1.71.9 90 88

Ocean38,000 Gt

6

Fossil Fuel4000 Gt

Permafrost 1466 Gt

Atmosphere750 Gt + 3 Gt yr-1

119120

Soils 1400 GtVegetation 600 Gt

Permafrost Carbon Burial

Permafrost Horizon

Deposition (loess, peat, erosion, volcanic)

Soil Depth

Active Layer

Permafrost

~1466 Gt C in permafrost [Tarnocai et al., 2009]

Permafrost Carbon

30,000 year old roots, Siberia [Zimov et al., 2006]Mammoth, Siberia

32,000 year old grass, Alaska 15,000 year old moss, North Slope [Schaefer , 2012]

Permafrost Carbon Feedback

Amplification of warming due to release of CO2 and CH4 from thawing permafrost

Methane Release from Thawing Permafrost

K. Walter [email protected]

Thaw bulb

Permafrost

Peat

Methane production

Methane emissionemission Thermokarst

Erosion

Dead plant & animal remains

Burning methane over a thermokarst lake in Siberia (K. Walter)

IPCC A1B Scenario

200

300

400

500

600

700

800

1960 2000 2040 2080 2120 2160 2200

Date (year)

Atm

osph

eric

CO

2 (pp

m)

Current Permafrost

Active Layer Thickness ALT (cm)Active Layer Thickness ALT (cm)

Projected Permafrost DegradationHadCM3 (med)HadCM3 (med)

Active Layer Thickness ALT (cm)Active Layer Thickness ALT (cm)

Projected Permafrost Loss

CCSM3 (low)CCSM3 (low)29% loss29% loss

HadCM3 (med)HadCM3 (med)50% loss50% loss

MIROC3.2 (high)MIROC3.2 (high)59% loss59% loss

Increase in ALT by 2200 (cm)Increase in ALT by 2200 (cm)

Permafrost Carbon Tipping Point

PCF Tipping Point 2023±4

Date (year)

Cum

ulat

ive

NE

E (

Gt C

)

Arctic switches from a sink to a source

Cumulative Permafrost Carbon Flux

Date (year)

Per

maf

rost

Car

bon

Flu

x (G

t C)

190±64 Gt

104±37 Gt

65±23% of cumulative global land sink (~160 Gt C)Equivalent to 87±29 ppm

Vostok Ice Core Records

• CO2 lags behind temperature by 600±400 yr

80 ppm

Paleo-Permafrost Carbon FeedbackPalaeocene-Eocene Thermal Maximum (PETM)

Orbit perturbations trigger Antarctic permafrost thaw [DeConto et al. 2011, in review]

PCF and Fossil Fuel Emissions

• Both inject old carbon into atmosphere• Both irreversible• A1B scenario: 700 ppm by 2100

• 1345 Gt C total emissions• 190 Gt C permafrost carbon flux• 1157 Gt C fossil fuel emissions

• Must reduce fossil fuel emissions by additional 15% or overshoot target climate

Conclusions

• PCF can explain past climate variability

• PCF tipping point in mid 2020s

• PCF is strong: 190±64 Gt C by 2200

• Emission reductions must account for PCF

• Tellus B paper: Schaefer et al. [2011]

Backup SlidesBackup Slides

The SiBCASA ModelThe SiBCASA Model

CO2 Temp

Humidity

NEE Latent Heat

Sensible Heat

Snow

R

Moi

stur

e

Tem

pera

tur

e

Car

bon

Canopy

Soil

GPP

Input Weather

Boundary Layer

Permafrost Carbon in SiBCASA

Dmin = max ALT during spinup

Active Layer Thickness (ALT)

Soil Carbon Pools

Dmax = 3 m

Active Layer

Permafrost

Thawed CarbonPermafrost

Carbon Pool

Active Layer

Permafrost Carbon Pool

Permafrost

• 313 Gt C in permafrost carbon pool• 91 Gt C in active layer• 414 Gt C in top 3 m (575 Gt C estimated*)

*Tarnocai et al. [2009]

Experiment Setup

• SiBCASA + ERA40 + A1B scenario

• Continuous/discontinuous permafrost

• 1973-2001: “spin up“

• 2002-2200: random ERA40 + linear trend• MIROC3.2 (high)• HadCM3 (med)• CCSM3 (low)

Estimating Uncertainty

• 18 ensemble members• 3 warming rates• 3 permafrost carbon densities• 2 sub-grid permafrost extents

• Best estimate: ensemble mean

• Uncertainty: ensemble standard deviation

IPCC A1B Arctic Temperatures

Air

Tem

pera

ture

(°C

)CCSM3 (low warming)HadCM3 (medium warming)MIRC3.2 (high warming)

Average air temperature for permafrost regions

Permafrost Area Loss

Date (year)

Per

maf

rost

Are

a (%

)

169±54 Gt C203±63 Gt C

213±65 Gt C

Frozen Ground ExtentFrozen Ground ExtentPermafrostSeasonally Frozen GroundIntermittently Frozen Ground

Zhang et al., 2003. EICOP

Snow Limit

Permafrost covers 24% of land surface in Northern Hemisphere

Atmosphere

Vegetation

Snow cover

Geothermal

Organic layer

Permafrost

Buffer Layer

What Drives Permafrost Formation?What Drives Permafrost Formation?

Barrow, Barrow, AlaskaAlaska

Observed Soil Temperature (C) 1996-7

Month

Soi

l Dep

th (

m)

Sno

w D

epth

(cm

)A

ir T

emp

(C)

Soil Temperature (C)

Observed Snow Depth (cm) 2002-3

Observed Air Temperature (C) 2003-4

Repeated Soil Freeze/Thaw Cycles Shape Permafrost Landscape

• Water expands ~9% when it freezes into iceWater expands ~9% when it freezes into ice

• Frost Heave: rising of ground surface when : rising of ground surface when ground water Freezesground water Freezes

• Thaw Settlement: settling of ground surface : settling of ground surface when ground ice meltswhen ground ice melts

• Moisture Movement: soil moisture moves from : soil moisture moves from unfrozen zone to frozen frontunfrozen zone to frozen front

Permafrost FeaturesPermafrost Features

Frost Heave, Yamal Stone Circles, Svalbard

Stone Circles, NW Territories Stripes, Glacier NP

Permafrost Degradation [IPCC, 2007]Permafrost Degradation [IPCC, 2007]

>3 °C increase mid-1950s to 1990

1 to 3 °C increase in past several

decades0 to 1 °C increase since 1970s

4 to 6 C increase in 20th Century2 to 3 C in last 30 years

-4

-3

-2

-1

0

1

2

3

4

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000Year

Tem

pera

ture

Ano

mal

y (°

C)

0.2 m; Trend = +0.78°C/decade0.4 m; Trend = +0.79°C/decade0.8 m; Trend = +0.65°C/decade1.6 m; Trend = +0.55°C/decade3.2 m; Trend = +0.66°C/decade

Russian Permafrost Temperature TrendsRussian Permafrost Temperature Trends

Frauenfeld et al. [2004] Zhang et al. [2005]

Russian Active Layer TrendsRussian Active Layer Trends

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Year

Act

ive

Lay

er D

epth

Ano

mal

y (m

) 1960–1998 Change: +25 cm

Frauenfeld et al. [2004] Zhang et al. [2005]

Talik DevelopmentTalik Development

Seasonally frozen ground

Talik

Permafrost

• Talik: Unfrozen soil layer above permafrost, but below seasonally frozen surface layer

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1950 1960 1970 1980 1990 2000Year

Soi

l Tem

pera

ture

(°C

)

Soil Temperature at 3.2 m in Central Siberia (°C)

Talik Forms

Permafrost CarbonPermafrost Carbon

• 1672 Gt C in permafrost 1672 Gt C in permafrost [[Tarnocai et al.Tarnocai et al., 2009], 2009]

• 750 Gt C in atmosphere 750 Gt C in atmosphere

Roots, Siberia [Zimov et al., 2006]

Humus, Siberia [Davis, 2000]Mammoth, Siberia

Projections of Permafrost DegradationProjections of Permafrost Degradation

• General Pattern: lose area from the south, General Pattern: lose area from the south, increase active layer thickness everywhereincrease active layer thickness everywhere

SourceReduction in

Permafrost Area by 2100 (%)

Increase in Active Layer

Thickness (cm)

Schaefer et al . [2010] 4 19-28Zhang et al . [2008] 16-19 30-80Saito et al . [2007] 60 100-300Lawrence and Slater [2005] 90 500Lawrence et al . [2008] 90 500

Feedbacks to AtmosphereFeedbacks to Atmosphere

• Energy balanceEnergy balance• Snow Albedo FeedbackSnow Albedo Feedback• Vegetation Albedo FeedbackVegetation Albedo Feedback• Sea Ice Loss and Arctic AmplificationSea Ice Loss and Arctic Amplification• Bowen ratio seasonalityBowen ratio seasonality

• Trace Gas FeedbacksTrace Gas Feedbacks• COCO22 Fertilization Fertilization• Permafrost Carbon FeedbackPermafrost Carbon Feedback

Net Ecosystem Exchange (NEE)Net Ecosystem Exchange (NEE)

• NEE < 0 means net carbon uptake

NEE = Respiration - Photosynthesis

Enhanced by Permafrost

Carbon Feedback

Enhanced by CO2

Fertilization

58±19 Gt C by 2200 is a lot of carbon58±19 Gt C by 2200 is a lot of carbon

• 3.5% of permafrost carbon3.5% of permafrost carbon

• 26±9 ppm26±9 ppm increase comparable increase comparable Vostok Ice Core (80 ppm)Vostok Ice Core (80 ppm)

• 13-27% of global land sink13-27% of global land sink

• 4±1% of fossil fuel emissions 4±1% of fossil fuel emissions for 700 ppm targetfor 700 ppm target

Walking Points on PermafrostWalking Points on Permafrost

• Freeze/thaw cycles shape the landscapeFreeze/thaw cycles shape the landscape

• Permafrost degradation has already startedPermafrost degradation has already started

• Permafrost Carbon Feedback will impact Permafrost Carbon Feedback will impact climate and fossil fuel reduction strategiesclimate and fossil fuel reduction strategies

When is the Permafrost Carbon Tipping Point?

Kevin Schaefer1, Tingjun Zhang1, Lori Bruhwiler2, Andrew P. Barrett1

1National Snow and Ice Data Center, University of Colorado2NOAA Earth System Research Laboratory

Observed Permafrost

Rock Circle Formation

Expand out in winter when frozen

Drop down in spring when thawed

Permafrost Area by Country

Permafrost Class by Country

Variations of area extent of seasonally frozen ground and snow in the Northern Hemisphere during the winter of 1998/99.

Seasonally Frozen Ground

Monthly maximum area extent of seasonally frozen ground

Seasonally frozen ground is ~65 x 106 km2 or 68% of the land area in the Northern Hemisphere.

Seasonally Frozen Ground

Climate/Weather

Geothermal heat flux

Ground temperature regime

Thermal diffusion equation

Soil thermal properties

Q* QH QLEQG = 0Soil moisture

conditions

Site-specific factors (albedo, roughness, slope, aspect, snow,

soil texture, etc.)

A Permafrost Model

Snow

Atmosphere

Lower Boundary

Frozen ground

Permafrost or unfrozen ground

Thawed ground

Moving phase plane: heat conduction with or without phase change

Moving phase plane

Heat conduction

Snow-soil interface: heat conduction with or without phase change

k = ks()

hs(t) = (x,t)

C= CFr(x,T)

k = kFr (x, T)

C= CFr (x,T)

T(Zfr ) = Tf

k = kTh (x, T)

C = CTh(x,T)

T(Zth ) = T f

Moving boundary: heat conduction in deforming medium

Boundary condition: Prescribed temperature, or heat flux, or surface energy balance

Boundary condition: prescribed temperature or heat flux

Modeling Permafrost

Permafrost classificationPermafrost classification• By area coverageBy area coverage

• Continuous (>90% of area)Continuous (>90% of area)• Discontinuous (50-90% of area)Discontinuous (50-90% of area)• Sporadic (10-50% of area)Sporadic (10-50% of area)• Isolated (<10% of area)Isolated (<10% of area)

• By Location:By Location:• Terrestrial Terrestrial • Sub-ice Sub-ice • Sub-sea Sub-sea • RelicRelic

• By Coupling with climate:By Coupling with climate:• Exposed (terrestrial)Exposed (terrestrial)• Submerged (sub-ice, sub-sea, and relic)Submerged (sub-ice, sub-sea, and relic)

Frozen Ground Data ProductsFrozen Ground Data Products• http://nsidc.org/fgdc

• Arctic EASE-Grid Freeze and Thaw Depths, 1901 - 2002• Arctic Soil Freeze/Thaw Status from SMMR and SSM/I,

Version 2• Circumpolar Active-Layer Permafrost System (CAPS)• Global Annual Freezing and Thawing Indices• Modeled Daily Thaw Depth and Frozen Ground Depth• Northern Hemisphere EASE-Grid Annual Freezing and

Thawing Indices, 1901 - 2002• Northern Hemisphere Seasonal and Intermittently Frozen

Ground Areas 1901-2001• Russian Historical Soil Temperature Data• Time Series of Active Layer Thickness in the Russian Arctic,

1915-1990• Circumpolar Active-Layer Permafrost System (CAPS)

Permafrost MonitoringPermafrost Monitoring

Permafrost Carbon in SiBCASA

permafrost carbon density is 2% by massDthreshold = 1973-2001 maximum active layer depthDactive = active layer depth

Slow (80%)

Metabolic (5%)

Structural (15%)

Soil Carbon PoolsDthreshold

Permafrost Carbon Pool

Dactive

Dthreshold

Dactive

Thawed Carbon

Permafrost Carbon Pool