From the description phase (month 1-18)… … to the understanding phase (month 19-36)

WP3: Long-term assessment

Major objective:Establish the framework for repeated anthropogenic CO2 (Cant) inventory quantification within the Atlantic Ocean basin, including its polar extensions and the European marginal seas

Description phase is in good hands but will still go on for quite some time…

• Interior ocean data to be submitted by Dec. 31, 2006;

• Database has grown tremendously to at least 4 times the size of the GLODAP data base;

• North, middle, and south groups have been formed and will start looking into quality and consistency issues; in about one year we should be able to see results;

•Cant method comparison is moving along, produces results, and may

eventually provide recommendations on methods to use (or at least to avoid);

• Cant methods have improved and appear to be converging.

WP3: Long-term assessment

Model A

Model B

Model C

Model D

Model E

…

Model-basedMethod A

Method B

Method C

Method D

Method E

…

Observation-based

Anthropogenic CO2

Things are going in the right way…

WP3: Long-term assessment

WP3: Long-term assessment

But need to bring surface CO2 fluxes and the interior ocean carbon storage together …

• How do these match quantitatively?

• What are the implications of changing CO2 disequilibria in the surface

ocean for the interior ocean carbon storage and our methods to detect them?

This is clearly the next step to go after we have done our homework …

WP3: Long-term assessment

But there is this parallel universe in CarboOcean that deals with biogeochemical feedbacks …

• pH-driven changes in calcification with potential impact on air-sea CO2 fluxes (i.e. surface saturation levels) and ballasting (i.e. biological

carbon pump;

• Increasing C:N Redfield ratios under elevated CO2 with potential

impact biological on carbon sequestration;

• Enhanced carbon exudation and formation of transparent exopolymer particles with potential impact on particle flux and deep carbon export;

• Effect of global warming on degradation and remineralization length scales with potential impact on the biological pump.

Maybe it is to early to worry about these feedbacks in a quantitative sense, but maybe not …

Method A

Method B

Method C

Method D

Method E

…

Model A

Model B

Model C

Model D

Model E

…

WP3: Long-term assessment

Method A

Method B

Method C

Method D

…Model A

Model B

Model C

Model D

…

Biogeochemical feedbacks

Air-sea CO2 fluxes

Whatdo we need to understand?

Whatdo we need to understand?

WP3: Long-term assessment

Will anthropogenic CO2 remain a useful quantity?

If the we can no longer treat anthropogenic CO2 as a transient tracer on top of a steady-state natural carbon background, what is the use of it?

What do our customers want to know – whether the increasingly ill-defined property ‘anthropogenic CO2’ is changing or the total carbon storage of the ocean?

Do we know what the observational approach to regularly assess the ocean carbon storage will look like?

Is there hope that models will eventually make an observational effort obsolete?