Open Ocean Modelling of the Carbon Cycle and Air-Sea CO 2 Fluxes

1 04/2003 © Crown copyright

Open Ocean Modelling of the Carbon Cycle and

Air-Sea CO2 Fluxes

Science Element 3a of CASIX

Steve Spall

(Met Office)


The Talk What are the aims? Who are the main contributors? What tools will we use? Some preliminary results What will we be developing? How we fit in with the rest of CASIX Measuring how well we are doing


Aims

Produce estimates of air-sea fluxes of CO2,

focused on the North Atlantic, using a high resolution GCM

Improve these estimates by assimilating Earth Observation data into the carbon cycle model

Integrate other developments under CASIX into the GCM to also improve the CO2 flux

estimates


The Main Contributors

Rosa BarcielaMet Office•Setting up the model•Performing model simulation•Looking at resolution sensitivity•Providing boundary data for shelf seas

Mike BellMet Office

•Oversee work with the FOAM model•Advise on aspects of FOAM

simulations•Advise on data assimilation

techniques•Member of the CASIX management

group


John HemmingsSOC•Develop assimilation techniques•Assess simulations including assimilation•Advise on and implement improvements to assimilation and the carbon cycle model

Ian TotterdellSOC

•Advise on implementation and improvements to the carbon cycle

model•Advise on data assimilation

techniques

Steve SpallMet Office

•Oversee work in this science element of CASIX •Advise on implementation of the carbon cycle

model•Integrate new improvements into the model

•Member of the CASIX Scientific Steering Committee


What tools will we use?

Coupling together two models…

– FOAM

»Forecasting Ocean Assimilation Model

– HadOCC

»Hadley Centre Ocean Carbon Cycle model


FOAM Can be run at different resolutions for different domains


HadOCC ‘NPZD’ ecosystem model

Coupled to carbon and alkalinity

Transported around the ocean by physical processes

Normally used for climate studies


Resolution Sensitivity

Eddies enhance biological uptake of carbon

Using FOAM at higher resolution may improve the simulation of air-sea CO2 fluxes

Nutrient supply driving biological carbon uptake

From a 1/3° North Atlantic Ocean Model

Enhanced eddies

Suppressed eddies

Control

Figure from Oschlies and Garcon (Nature, 1998)


Preliminary Results

Comparison of SeaWiFS chlorophyll against the model

Run for early 2000 Some encouraging

results, some work to do



What will we be developing? HadOCC integrated into FOAM and

demonstrated at different resolutions Assimilation methods for Ocean Colour in

the ocean carbon cycle model 10 year hind-cast simulation to provide

estimates of air-sea CO2 fluxes

Improved assimilation methods, making use of new Earth Observation products where available


How we fit in with the rest of CASIX

Provide boundary conditions for shelf seas models

Implement new parameterisations of air-sea gas exchange

Integrate developments from interface modelling

Provide estimates of air-sea CO2

fluxes for the development of climatologies


Measuring how we are doing

Useful to measure how well the model is doing

Good quantity to test is ocean pCO2

A useful graphical representation is a Taylor diagram

An example of a measure of model accuracy


Taylor Diagrams Take a data set and

sub-sample the model Plot the correlation

between model and data and the ratio of standard deviations

Want to move towards the point ‘Obs’


Summary Coupling of the HadOCC ocean carbon cycle

model into the Met Office open ocean forecasting model

Aim is to provide hind-cast estimates of air-sea CO2 fluxes

Develop assimilation for the ocean carbon cycle to improve these estimates

Integrate developments from other elements of CASIX

Documents

Open Ocean Modelling of the Carbon Cycle and Air-Sea CO 2 Fluxes