Understanding the Ocean Carbon Cycle

from Atmospheric Measurements of O2 and CO2

Andrew Manning, UEA, UK

Year

1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006

CO

2 co

ncen

trat

ion

(ppm

)

310314318322326330334338342346350354358362366370374378382

Mauna Loa CO2

South Pole CO2

Dave Keeling

The Keeling Curve

Year

1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006

O2/

N2

ratio

(pp

m E

q)

-80-76-72-68-64-60-56-52-48-44-40-36-32-28-24-20-16-12-8

CO

2 co

ncen

trat

ion

(ppm

)

310314318322326330334338342346350354358362366370374378382

Mauna Loa CO2

South Pole CO2

Mauna Loa O2

South Pole O2

Dave Keeling

Ralph Keeling

The Keeling Curves

Simplified Global Budgets:CO2 = F – O – L

Atmosphere-Oceangas exchange

Photosynthesis Respiration

Fossil fuel burning

Simplified global CO2 cycle

F = fossil fuel carbon emissionsO = net oceanic carbon sinkL = net land biotic carbon sink

+ Z

Z = net oceanic O2 source

O2 = –FF + LL

F = average fossil fuel O2:CO2 ratioL = average land biotic O2:CO2 ratio

and O2 cycles

(CO2)global (ppm)354 358 362 366 370 374 378 382 386

(O2/

N2)

glo

bal (

per

meg

)

-360

-340

-320

-300

-280

-260

-240

-220

-200

-180

-160

-140

-120

-100

Jan. 1993

change due to fossil fuelcombustion only

Jan. 2003

Atmosphericchange

Quantifying global oceanic and land biotic carbon sinks

Manning, 2001& IPCC TAR, 2001

Manning & Keeling, Tellus, 2006& IPCC AR4 draft, 2006

Units: Pg C yr-1

1990-2000 1993-2003Fossil-fuel emissions: 6.3 ± 0.4 6.5 ± 0.4Atmospheric CO2 increase: 3.2 ± 0.1 3.7 ± 0.1Net oceanic carbon sink: 1.7 ± 0.5 2.2 ± 0.6Net land biotic carbon sink: 1.4 ± 0.7 0.5 ± 0.7

O2 = –FF + LL + Z

CO2 = F – O – L(CO2)global (ppm)354 358 362 366 370 374 378 382 386

(O2/

N2)

glo

bal (

per

meg

)

-360

-340

-320

-300

-280

-260

-240

-220

-200

-180

-160

-140

-120

-100

Jan. 1993

change due to fossil fuelcombustion only

Jan. 2003

Ocean uptake

Atmosphericchange

Terrestrial uptake

Ocean O2 outgassing

Quantifying global oceanic and land biotic carbon sinks

ALT (82°N, 63°W)

89 90 91 92 93 94 95 96 97 98 99 00 01 02 03

AP

O (

pe

r m

eg

)

-210

-180

-150

-120

-90

-60

-30

0

APO - Atmospheric Potential Oxygen

APO = O2 + LCO2

APO is conservative with respect to land biotic processes

So APO variations result only from:

- oceanic CO2 sink (long term)

- oceanic O2 fluxes (short term)

ALT (82°N, 63°W)

89 90 91 92 93 94 95 96 97 98 99 00 01 02 03

CO

2 c

on

cen

tra

tion

(p

pm

)

346350354358362366370374378382

ALT (82°N, 63°W)

89 90 91 92 93 94 95 96 97 98 99 00 01 02 03O

2/N

2 r

atio

(p

er

me

g)

-360-320-280-240-200-160-120

-80-40

0

From atmospheric O2 (APO) observations and transport model inversion get FO2

(oceanic O2 flux).

Then calculate kg2 from: FO2 = kg2 [ pO2(oc) – pO2(atm)]

Use this kg2 with CO2 observations to derive air-sea CO2 fluxes with less uncertainty.

Wanninkhof and McGillis, GRL, 1999

Gas exchange velocities from APO measurements Regional quantification of ocean carbon sinks

FCO2 = kg1[pCO2(oc) –

pCO2(atm)]

Large uncertainties in kg1

Large uncertainties in calculated air-sea CO2 fluxes.

Stephens et al., GBC, 1998

Gruber et al., GBC, 2001

Latidudinal distribtion of APO fluxes Validation and improvement of ocean BGC models

Battle et al., GBC, 2006

Tohjima et al., GRL, 2005

DurbanDurban

FelixstoweFelixstowe

Felixstowe to DurbanPeriodicity = 45 days

8 cruises/yr

CarboOcean atmospheric O2/CO2 measurements

-500

-450

-400

-350

-300

-250

-200

-150

-100

19Aug 20Aug 21Aug 22Aug 23Aug 24Aug 25Aug 26Aug 27Aug 28Aug 29Aug 30Aug 31Aug 01Sep 02Sep 03Sep 04Sep

Day in 2006

O2

(per

meg

)

360

365

370

375

380

385

CO

2 (pp

m)

O2CO22 hr moving averages

See poster by Michael Patecki for more info

Atmospheric O2/CO2 measurements in CarboOcean:

Michael Patecki, UEA, U.K.Poster: System development and preliminary results of atmospheric O2 and CO2 from shipboard measurements in the North Atlantic Ocean.

Jost Lavric, LSCE, FrancePoster: Continuous high accuracy atmospheric O2/N2 and CO2 measurement – a new automatic station on Cape Farewell, Southern Greenland.

Ingrid Luijkx, RuG, The NetherlandsPoster: Continuous atmospheric CO2 and O2 measurements on the F3 North Sea gas and oil platform.

Harro Meijer, RuG, The Netherlands

1) Atlantic O2 + CO2 measurementsa) CarboOcean, with Michael Patecki

Continuous, automated measurements, achieved with:- “Oxzilla” fuel cell O2 analyser - Siemens NDIR CO2 analyser- “Blue Box” for calib. gases- 2-stage drying system

Stephens et al. (1998)

Gruber et al. (2001)

Lack of O2 observation!

CO2

Month

50N-40N

40N-30N

30N-20N

20N-10N

10N-EQ

EQ-10S

10S-20S

20S-30S

10 ppm

1 3 5 7 9 11

30S-40S

O2/N

2

Month

50 per meg

1 3 5 7 9 11

APO

Month

50 per meg

1 3 5 7 9 11

Data and figure courtesy of Y. Tohjima, NIES, Japan

Pacific Ocean shipboard flask measurements, 2002-2004

40S

20S

0

20N

40N

60N

120E 180 120W 60W

PYXISGolden WattleMOL GloryFujitrans World

-250

-200

-150

-100

-50

0

30N-20N

2002 2003 2004

O2/

N2

(per

meg

)

APO interannual variabilitym

ol O

2/y

r x1

01

4

- ocean models under-estimate observed variability

Buitenhuis, Le Quéré, Keeling

Simplified Global Budgets:CO2 = F – O – L

Atmosphere-Oceangas exchange

Photosynthesis Respiration

Fossil fuel burning

Simplified global CO2 and O2 cycles

F = fossil fuel carbon emissionsO = net oceanic carbon sinkL = net land biotic carbon sink

O2 = –FF + LL

F = average fossil fuel O2:CO2 ratioL = average land biotic O2:CO2 ratio

+ Z

Z = net oceanic O2 source

APO - Atmospheric Potential Oxygen

(CO2 = F – O – L ) x L

+O2 = –FF + LL + Z

APO Fossil fuel APO loss

Oceanic APO loss

O2 + LCO2 = (L – F)F – (LO – Z)

1) Solve ‘O’ with APO

2) Solve ‘L’ with CO2

- land sink more variable, and have larger CO2 network

- less “noise” in long-term APO trend

CO2

O2

Atmosphere

Ocean

O2

CO2

Relative reservoir sizes Long-term trends

O2

CO2

Seasonal effects

CO2

O2

Keeling and Garcia, PNAS, 2002.

CarboOcean – observations theme led by UEA- 5 year, 15 million Euro programme-main objective: to quantify net annual air-quantify net annual air-sea COsea CO2 2 fluxes in North Atlantic Ocean fluxes in North Atlantic Ocean (and (and world ocean)world ocean)

My contribution:continuous, automated system for measurements of atmospheric O2 and CO2 from ships(to complement measurements of dissolved O2 and CO2)

FelixstoweAntwerp

Gran Canaria

Cape Town

Port Elizabeth

Durban

Felixstowe to Durban

Periodicity: Felixstowe is visited every 45 days