12th, Jan. 2017
9th GEOSS Asia-Pacific Symposium

Evaluation of oceanic CO2 uptake
based on global pCO2 observation
database “SOCAT”
National Institute for Environmental Studies
Center for Global Environmental ResearchShin-ichiro Nakaoka

Motivations for pCO2 observation

Anthropogenic oceanic
CO2 exchange:-1.6 ± 0.9 PgC yr-1
Fig. Climatological annual mean sea-air CO2 flux distribution

Takahashi et al. (2009, DSR II)・ Long-term (~35yr) monthly mean pCO2 and sea-air CO2 flux
Knowledge of their Inter-annual variability are still insufficient環境研のVolunteer
Observing Ships (VOS)
観測
NIES VOS measurementsfor CO2(2006 - )Pros・Frequent measurements
・(relatively) low cost

Cons・Difficult to make obs. in hydrographic cast・Obs. routes depends on country’s tradecircumstances

Combination of VOS and research vessel’s observations is crucial.

環境研のVolunteer
Observing Ships for(VOS)
観測
NIES VOS measurements
pCO2
New Century 2(Kagoshima-senpaku Co.)

Trans Future 5 (Toyofuji Shipping Co.)

Course：Toyohashi〜U.S west/east cst.
Term：4 （west cst.）〜８ weeks（east cst.）
Start since：Apr. 2014〜

Course：Nagoya〜Aus.〜NZ
Term：６ weeks
Start since : Feb. 2006〜

環境研のVolunteer
Observing Ships for(VOS)
観測NIES VOS measurements
pCO2

International pCO2 database “SOCAT”
Downloadable at http://socat.info in text, NetCDF, ODV, Matlab
290 320350380

410 440 (µatm)

1957-2015
V4, A-D

pCO2 values (yr-1)

260

x 106

2.0
A-D

1.00.0
1960

1970

1980

1990

2000

2010

Global synthesis and gridded products of surface ocean pCO2 or fCO2 (fugacityof CO2) in uniform format with quality control;Interactive online viewers;V4: 18.5 million fCO2 values, accuracy < 5 μatm from 1957-2015 (flags of A-D);
Plus calibrated sensor data (< 10 μatm, flag of E);
Documented in ESSD articles;
Community activity with >100 contributors worldwide.
Bakker et al. (2016) ESSD

International pCO2 database “SOCAT”

International pCO2 database “SOCAT”

International pCO2 database “SOCAT”

Internationaldatabase“SOCAT”
Surface pCO
water2 fCO
perdecade(v4)
2260

280

300

ec

320

340

1957-69

360

380

400

420

440 (µatm)

1970s
Increase in pCO2 datacollection from 1990s
onwards.

ec

1980s

1990s2000s

2010-15

pCO2 are not sampled in the
Indian Ocean after 2000.

(after Bakker et al., 2016 ESSD)
www.socat.info

pCO2 Mapping and evaluation of CO2 flux

Mapping techniques

1957-2015
V4

Flux = k * ΔpCO2(w-a)
Gas transfer parameterisation,wind speed productA synthesis data productpCO2 products

after Bakker et al., 2016 ESSD
Air-sea CO2 flux products

Pacific: Nakaoka et al., 2013, BG; Ishii et al., 2014, BG
Global: Rödenbeck et al., 2015, BG
Landschützer et al., 2014, GBC, 2015, SciencepCO2 Mapping and evaluation of CO2 fluxpCO2sea = fSOM(x, y, z, SST, SSS, MLD, CHL) + α (t-tref)

Rödenbeck et al. (2015)

pCO2 Mapping and evaluation of CO2 flux
F = s・k・∆pCO2 = s・k・(pCO2sea – pCO2air)

Rödenbeck et al. (2015)

pCO2 Mapping and evaluation of CO2 flux
Increasing oceanic CO2 uptake

Rödenbeck et al. (2014, BG)
Landschützer et al. (2015, Science)

Le Quere et al. (2016 ESSD)

Future SOCAT versions
NEW data

Months of the yearwith fCO2 values(1970-2014) (V3)
(Bakker et al., 2016 ESSD)

V5 Data submission ends 15 January 2017;
V5 Quality control ends 31 March 2017;
V5 Release in summer 2017;
V6: V5 dates + 1 year

www.socat.info

Summary・ NIES has measured atmospheric and oceanic CO2 since 1995
using VOS with cooperation of shipping companies.
・ NIES plays a role in SOCAT as a data provider as well as aquality controller for the North Pacific.
・ SOCAT is a helpful tool for understanding observed pCO2
variation and it is available to the public.
・ While a lot of pCO2 measurements has been made, there is stillless observation in the eastern equatorial Pacific and in theIndian Ocean after 2000.
・ Products of pCO2 distribution using SOCAT are proposed in
SOCOM project.
・ Oceanic CO2 uptake increases rapidly after 2010.

Acknowledgements
SOCAT is an international effort, supported by the International
Ocean Carbon Coordination Project (IOCCP), the Surface OceanLower Atmosphere Study (SOLAS), and the Integrated Marine
Biogeochemistry and Ecosystem Research (IMBER) program.
The many researchers and funding agencies responsible for thecollecting data and quality control are thankful for theircontributions to SOCAT.

Thank you for your attention!