1 04/2003 © Crown copyright Open Ocean Modelling of the Carbon Cycle and Air-Sea CO 2 Fluxes Science Element 3a of CASIX Steve Spall (Met Office)

2 04/2003 © Crown copyright 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

3 04/2003 © Crown copyright Aims Produce estimates of air-sea fluxes of CO 2, 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 CO 2 flux estimates

4 04/2003 © Crown copyright The Main Contributors Rosa Barciela Met Office Setting up the model Performing model simulation Looking at resolution sensitivity Providing boundary data for shelf seas Mike Bell Met Office Oversee work with the FOAM model Advise on aspects of FOAM simulations Advise on data assimilation techniques Member of the CASIX management group

5 04/2003 © Crown copyright John Hemmings SOC Develop assimilation techniques Assess simulations including assimilation Advise on and implement improvements to assimilation and the carbon cycle model Ian Totterdell SOC Advise on implementation and improvements to the carbon cycle model Advise on data assimilation techniques Steve Spall Met 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

6 04/2003 © Crown copyright What tools will we use? Coupling together two models… –FOAM »Forecasting Ocean Assimilation Model –HadOCC »Hadley Centre Ocean Carbon Cycle model

7 04/2003 © Crown copyright FOAM Can be run at different resolutions for different domains

8 04/2003 © Crown copyright HadOCC ‘NPZD’ ecosystem model Coupled to carbon and alkalinity Transported around the ocean by physical processes Normally used for climate studies

9 04/2003 © Crown copyright Resolution Sensitivity Eddies enhance biological uptake of carbon Using FOAM at higher resolution may improve the simulation of air- sea CO 2 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)

10 04/2003 © Crown copyright Preliminary Results Comparison of SeaWiFS chlorophyll against the model Run for early 2000 Some encouraging results, some work to do

11 04/2003 © Crown copyright

12 04/2003 © Crown copyright 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 CO 2 fluxes Improved assimilation methods, making use of new Earth Observation products where available

13 04/2003 © Crown copyright 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 CO 2 fluxes for the development of climatologies

14 04/2003 © Crown copyright Measuring how we are doing Useful to measure how well the model is doing Good quantity to test is ocean pCO 2 A useful graphical representation is a Taylor diagram An example of a measure of model accuracy

15 04/2003 © Crown copyright 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’

16 04/2003 © Crown copyright 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 CO 2 fluxes Develop assimilation for the ocean carbon cycle to improve these estimates Integrate developments from other elements of CASIX