Determining the magnitude and variability of the anthropogenic CO2 uptake rate by

the oceans.

• Dick Feely (NOAA/PMEL/JISAO)

• Chris Sabine (NOAA/PMEL/JISAO)

• Rolf Sonnerup (JISAO/PMEL)

• Paul Quay (UW/JISAO)

JISAO/PMEL/UW Collaboration

• Observational Program (Feely, Sabine, Quay)

– Measuring pCO2, dissolved inorganic carbon (DIC), alkalinity, 13C/12C of DIC (δ13C)

– Using research cruises, volunteer observing ships (VOS), and moorings

• Modeling Program (Sonnerup)

– Using GCMs to simulate anthropogenic CO2, 13C/12C perturbations

Estimates of Global CO2 Sources & Sinks

Table 1. Global CO2 budgets (in PgC/yr) for the last twodecades based upon atmospheric CO2 and O2 dataa

Source or Sink 1980 to 1990 1990 to 1997

CO2 Emissions (Fossil fuel, Cement) 5.4 ± 0.3 6.4 ± 0.4

Atmospheric Increase 3.3 ± 0.1 3.2 ± 0.1

Ocean-Atmosphere Flux -1.9 ± 0.6 -1.7 ± 0.5

Land-Atmosphere Flux -0.2 ± 0.7 -1.4 ± 0.6

aPositive values represent fluxes to the atmosphere; negative values represent uptake away from the

atmosphere. The land-atmosphere flux represents the net balance of a positive term due to land usechanges and a negative term due to a residual carbon sink. Source: Prentice et al. (2001) IPCCReport

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Scientific Objectives• Estimate the rate of increase in the amount of

anthropogenic CO2 in the ocean. (research cruises)

• Estimate the net air-sea flux of CO2. (VOS+moorings)

• Determine whether the US coastal ocean is a source or sink for CO2. (research cruises + moorings)

• Separate natural variations from anthropogenic change in

ocean CO2. (data synthesis + models)

• Determine how changes in physical, chemical and biological processes affect the CO2 uptake rate. (models)

CLIVAR/CO2 Repeat Hydrography Program

We mus understand the temporal and spatial changes of the global ocean carbon system and the feedbacks to the climate system.

VOS Cruise Tracks (IOCCP)

Space and time coverage of ocean carbon observing networks

time

space1 m2 1 km2 GlobeOcean

BasinRegional(106 km2)

centuries

decadal

Inter-annual

seasonal

daily

Remote sensing

hourly

Process Studies

Repeat Trans-basin

Sections

VOS

surface pCO2

Shipboard

Time-Series

Moored

Time-Series

time

space1 m2 1 km2 GlobeOcean

BasinRegional(106 km2)

centuries

decadal

Inter-annual

seasonal

daily

Remote sensing

hourly

Process Studies

Repeat Trans-basin

Sections

VOS

surface pCO2

Shipboard

Time-Series

Moored

Time-Series

Rate of CO2 Increase

• Atmospheric CO2 is currently at 375 ppm (vs pre-industrial 280 ppm) and has been increasing by about 2 ppm per year over the last decade.

• Surface ocean in equilibrium with atmosphere would increase CO2 by 10 μmole/kg per decade.

~ 0.5% of background DIC concentration.

Rate of 13C/12C (δ13C) decrease

• The δ13C of atmospheric CO2 today is –8.1 ‰ (versus –6.4 ‰ in pre-industrial era) and decreasing at 0.2 ‰ per decade.

- δ13C of CO2 from fossil fuel combustion is -28 ‰.

• Surface ocean δ13C in equilibrium with atmosphere would decrease at 0.2 ‰ per decade.

• The magnitude of oceanic δ13C decrease is proportional to anthropogenic CO2 uptake.

Because the ocean mixes slowly, half of the anthropogenic CO2 stored in the ocean is found in the upper 10% of the ocean.

Average penetration

depth 1000 m

50% of 50% of anthropogenic anthropogenic

COCO22 in the in the ocean is ocean is

shallower than shallower than 400 m400 m

-40

-20

0

20

40

1970 1975 1980 1985 1990 1995 2000

Year

Geosecs (1973)

P16N (1991)

ENP81 (1981)

P15N (1994)

P2 (1994)

NOPP (1999)P1 (1999)

CO2 in the mixed layer1.3 ± 0.19 µmol kg-1 yr -1

r2=0.95n=7

-1

Feely et al. (submitted)

DIC increase in the mixed layer of the North Pacific Ocean

Seasonal and interannual changes in DIC and δ13C at Stn ALOHA (23°N 153°W)

Princeton MOM vs Observations

Changes in DIC and δ13C between 1993 and 2003 in the N. Atlantic (Repeat of A16N)

0.8

1

1.2

1.4

1.6

1.8

2

-10 0 10 20 30 40 50 60 70

Latitude

del1

3C (o

/oo)

July 1993

July 2003

0

1900

1950

2000

2050

2100

2150

-10 0 10 20 30 40 50 60 70

Latitude

DIC

coul

o (u

mol

/kg)

July 1993

July 2003

2003WHOI

GCM Simulated 13C Change (2003-1993)

(‰)