Carbon Cycle

Introduction

Inez Fung

UC BerkeleyIfung@berkeley.edu

2nd NCAR-MSRI Summer Graduate Workshop on Carbon

Data Assimilation

NCAR July 9-13 2006

High-precision Atm

CO2: at MLO since

1958

• 180 ppmv Last

Glacial Maximum

• 280 ppmv in the

preindustrial

(~1800AD)

• 380 ppmv in 2005

Units

3 3C air

C air

14 2

2 18mb

6

C( kgC / m ) ( kgAir / m ) ( MWt / MWt )

MWt 12gm / mole; MWt 29gm / mole

Area dxdydz 5 10 ( m )

100PMassAtm dxdydz ( kgAir / m ) Area ~ 5 10 kgAir

g

12MassC( 300 ppmv )

X( moleC / moleAir )

MassAtm ( 300 x10 ) ( )29

~ 60

=

= =

= =

= =

=

12

1PgC 0.5 p

0 10 kg 6

pmv( mi

00PgC 600GtC

xed _entireAtm )

= =

Outstanding Questions

• Only half of the CO2

produced by human

activities is remaining in

the atmosphere

• Where are the sinks that

are absorbing over 40% of

the CO2 that we emit?

– Land or ocean?

– Eurasia/North America?

• Why does CO2 buildup

vary dramatically with

nearly uniform emissions?

• How will CO2 sinks

respond to climate

change?

Continuous Carbon Cycling

• Fluxes PgC/yr

• Inventory PgC

• Turnover time

=

Inventory/Flux

• Atm CO2 --> inventory

• Land: turnover time 101-102 yrs. Ocean: turnover time 102-103 yrs

• Difficult (time consuming and expensive) to measure changes in land

and ocean inventories. Focus on fluxes

Conservation of Carbon in Atm

{ {{

Atm _transport mixing

z 0

SourcesSinChem P

kr od

s

SC

( )t

C P=

+

+ +=

oa b bao a a( F FLandUs )eS )F ( F FF= + + +

bao ba a ao( F F

C C C

( F F

'

C ) )( ) +

= +

=

Separate out background (pre-industrial) from the

perturbation (last 200 years) carbon cycle:

Pre-industrial:

Conservation of Perturbation Carbon in Atm

{ {{

Atm _transport mixing

z 0

SourcesSinChem P

kr od

s

SC

( )t

C P=

+

+ +=

oa b bao a a( F FLandUs )eS )F ( F FF= + + +

In later lectures, the conservations equation may appear as:

b i 1 a iT ( t ) M [T ( t )]+ =

i 1 i( x ) ux G( )+ = +

Kalnay:

Nychka:

Conservation of Perturbation Carbon in Atm

{ {{

Atm _transport mixing

z 0

SourcesSinChem P

kr od

s

SC

( )t

C P=

+

+ +=

oa b bao a a( F FLandUs )eS )F ( F FF= + + +

Fossil Fuel Emission

>95% emission in

Northern Hemisphere

Atm CO2 Signature of Fossil Fuel Emission:

N-S gradient

Conservation of Perturbation Carbon in Atm

{ {{

Atm _transport mixing

z 0

SourcesSinChem P

kr od

s

SC

( )t

C P=

+

+ +=

oa b bao a a( F FLandUs )eS )F ( F FF= + + +

Terrestrial Carbon Cycle

• Growth, mortality, decay

• GPP: Gross Primary

Productivity (climate,

CO2, soil H2O, resource

limitation)

• Ra: Autotrophic

respiration (T, live

mass,…)

• Rh: Heterotrophic

respiration: Decay (T,

soil H2O,..)

• NPP=GPP-Ra

120 PgC/yr 60 60

1200 PgC

800 PgC

GPP Ra Rh

Deforestation

Tough to estimate

• deforested area

• Carbon inventory before

deforestation

• Fate of removed carbon

• Fate of litter and soil carbon

Tough to discriminate atm

CO2 signature

Veg Type(x,y)

annual

mean NPP(x,y)

NDVI-seasonal

August 2000

February 2001

Satellite

Greenness

index: NDVI

Seasonality

of NPP

Seasonality of

Respiration not

well-defined

Net flux not

well-defined at

every location

Impact on Atmospheric CO2

Photosynthesis

Respiration

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Jan Dec

From Atm

To Atm

CO

2 F

lux

• Seasonal asynchrony

between photosynthesis and

decomposition

net fluxes of CO2 to and

from atm

seasonal cycle of CO2 in

atm

• Annual imbalance carbon

source/sink

Atmospheric CO2 Signature of Ecosystem C

Exchange: Seasonal Cycle

Mauna Loa, HawaiiPt. Barrow, Alaska

6.5 ppmv 16 ppmv

Source:

NOAA/CMDL

• Amplitude of atmospheric CO2 seasonal cycle increases poleward:

telecoping of growing season and greater asynchroneity bet’ fluxes

• Growing season net flux ~15-20% of annual NPP

Conservation of Perturbation Carbon in Atm

{ {{

Atm _transport mixing

z 0

SourcesSinChem P

kr od

s

SC

( )t

C P=

+

+ +=

oa b bao a a( F FLandUs )eS )F ( F FF= + + +

Ocean C from the Atm’s Perspective:

DIC = CO2* + HCO3

- + CO3=

1-2 % 80-90%

CO2

DIC, NO3

depth

atm

remineralizatio

n

photosyn

100 Pg C/yr

{ {oa aoGasExchRate( m / s ) so lub ility(T )mol

atm _ssfc _ocn

e /

f

m3

c

C

CO2* pCOF k )2F (=1442443

Marine

Productivity

Is possible when

upwelling brings:

•Nutrients from below

to euphotic zone

•Cold water

Small Flux, small inventory

of organic C

But alters DIC(z)

-Global baseline (hydrography, transient tracers,nutrients, carbonate system)-Improved analytical techniques for inorganic carbonand alkalinity (±1-3 μmol/kg or 0.05 to 0.15%)-Certified Reference Materials-Data management, quality control, & public data access

JGOFS/WOCE global survey (1980s and 1990s)

OceanC : Mainly

Dissolved Inorganic

Carbon (DIC)

Biology and DIC:

•Depletion near sfc

•Enrichment at

Depth

Latitude N

Dep

th

Atlantic Pacific

Conveyor Belt Transport of

DIC:

•Southward in Atlantic

•Northward in Pacific

Ocn currents ~ cm/s

Time scale ~ 103 yr

Air-Sea Fluxes of CO2

{ {

ocn oa ao

sfc _ocn atm _sfcGasExchRate( m / s ) so lub ility(T )moleC / m3

F F F

k (CO2* pCO2 )

=

=1442443

SUMMARY

{ {z 0

SourcesSinksAtm _transport mixing

boa ao a ab

S

S

(C )

( FLandUse ( F F

C

))

t

FF F

+

=+ =

= + + +

FF: mainly NH, relatively aseasonal

LandUse: mainly source tropics, sink in mid-latitudes

Ocean: outgassing in equatorial oceans, absorption

at mid-hi latitudes (in summer. Not sure about winter)

Vegetation and soils: annual mean fluxes~0 locally,

fluxes have large diurnal (~100 ppmv) and seasonal

ranges (~30 ppmv)

Atm CO2 data for assimilation

Atm CO2 Observations

• In situ: tower, continuous

• Flask: 2m, twice weekly, ~102 locations

• >400m Tall Tower: 11, 30, 76, 122, 244

and 396 m; Continuous

• Aircraft data

• Very few obs over land (CO2 very

variable)

• Upcoming: satellite data, column, (106

locations twice weekly)

WLEF, Park Falls, Wisconsin

Mauna Loa, Hawaii

In-situ Atmospheric Observing Network

Discrete surfaceflasks (~weekly)

Continuoussurface (hourly)observatories

Tall towerscontinuous(hourly)

Aircraftprofiles(~weekly)

Global Distribution of CO2 in the lower

troposphere

• secular trend

• N-S gradient

• Seasonal cycle

• Interannual variations

CO2 Concentration in the Outer Damon Room, NCARMesa Lab, 2/7 – 2/9/06

CC

SM

Clim

ate

Wo

rkin

g G

rou

pBoard of Trustees

ReceptionNational Science

Board Breakfast

ASP Reviews

Surface Observatories

Where both

insitu

(hourly) and

flask

(biweekly)

data are

taken:

Diurnal and

weather

cycles on top

of seasonal

cycles

Seasonal CO2: Continental vs Oceanic Sites

•CO2 seasonal cycle attenuate, but still coherent, far away

from source/sink region

•Peak-trough amplitude of seasonal cycle ~ 30 ppmv

(~10%)

Diurnal CO2: Highly variable in boundary layer

10 11 12 13 14 15 16 17

345

355

365

375

385

395

405

340

350

360

370

0-396 m Column Integral

WLEF Tall Tower, Park Falls, WI

11 m 30 m 76 m122 m244 m396 m

(Peter Bakwin, CMDL, 2001)•Diurnal cycle of photosynthesis and respiration

> 60 ppmv (20%) diurnal cycle near surface

•Varying heights of the planetary boundary layer (varying mixing volumes)

Calm night:

stably stratified

boundary layer

Well-mixed

PBL

Vertical Profiles (free troposphere)

384

372

20062005 DATE

AircraftCampaigns

COBRA 2000

Surface Fluxes => Atmospheric CO2

Orbiting Carbon Observatory(Planned Dec 2008 launch)

• Estimatedaccuracy forsingle column~1.6 ppmv

• 1 x 1.5 kmIFOV

• 10 pixel wideswath

• 105 minute polarorbit

• 26º spacing inlongitudebetween swaths

• 16-day returntime

Multiple Time/Space Scales g

GCM CarbonCentury

Decade

Year

Day

Hour

TIM

E

Plot Tower Landscape Region Continent Globe

1-D

BGC

Tower

Flux

Aircraft Flux

Satellite GPP, NPP

Tower

Footprint

Orbiting

Carbon

Observatory

Atmospheric

Inversion

SPACE

GCM CarbonCentury

Decade

Year

Day

Hour

TIM

E

Plot Tower Landscape Region Continent Globe

1-D

BGC

Tower

Flux

Aircraft Flux

Satellite GPP, NPP

Tower

Footprint

Orbiting

Carbon

Observatory

Atmospheric

Inversion

SPACE