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Open Ocean Modelling of the Carbon Cycle and
Air-Sea CO2 Fluxes
Science Element 3a of CASIX
Steve Spall
(Met Office)
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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
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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
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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
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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
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What tools will we use?
Coupling together two models…
– FOAM
»Forecasting Ocean Assimilation Model
– HadOCC
»Hadley Centre Ocean Carbon Cycle model
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FOAM Can be run at different resolutions for different domains
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HadOCC ‘NPZD’ ecosystem model
Coupled to carbon and alkalinity
Transported around the ocean by physical processes
Normally used for climate studies
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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)
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Preliminary Results
Comparison of SeaWiFS chlorophyll against the model
Run for early 2000 Some encouraging
results, some work to do
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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
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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
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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
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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’
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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