Representing Climate Feedbacks in Biogeochemical Ocean GCMs

2. High resolution physics particularly important when trying to resolve short time scales.High resolution physics particularly important when trying to resolve short time scales.

3. We can study the biology of all the individual parts of the system, but we then need to bring them together into a whole.We can study the biology of all the individual parts of the system, but we then need to bring them together into a whole.

8. Start with export vectors � pellets, marine snow, DOMStart with export vectors � pellets, marine snow, DOM

10. The DMS cycle Shown here is a diagram of the so called CLAW hypothesis, named after the initials of the authors of the Charlson et al. Nature paper in 1987. The diagram is taken from that paper. The first sentence summarises the hypothesis, i.e. that DMS from the ocean influences cloud properties which then feedback to the plankton community. In the diagram we have ocean DMS emissions being oxidised in the atmosphere, which through the atmospheric chemistry can become sulphate aerosol. The aerosol acts as cloud condensation nucleii and can change the cloud properties. The feedback operates though the change in cloud albedo, changing the solar irradiance reaching the ocean beneath the cloud and changing the surface temperature. This talk is about our attempt at the Hadley Centre to model this feedback loop using a numerical climate model.Shown here is a diagram of the so called CLAW hypothesis, named after the initials of the authors of the Charlson et al. Nature paper in 1987. The diagram is taken from that paper. The first sentence summarises the hypothesis, i.e. that DMS from the ocean influences cloud properties which then feedback to the plankton community. In the diagram we have ocean DMS emissions being oxidised in the atmosphere, which through the atmospheric chemistry can become sulphate aerosol. The aerosol acts as cloud condensation nucleii and can change the cloud properties. The feedback operates though the change in cloud albedo, changing the solar irradiance reaching the ocean beneath the cloud and changing the surface temperature. This talk is about our attempt at the Hadley Centre to model this feedback loop using a numerical climate model.

11. Justification is simple: different groups of phytoplankton may be subtly involved in various climate feedbacks. Justification is simple: different groups of phytoplankton may be subtly involved in various climate feedbacks.

12. You may laugh, but it�s useful to consider extremes.You may laugh, but it�s useful to consider extremes.

25. Tube feeding on a ciliateTube feeding on a ciliate

31. Note single bacteria compartment. But different bacteria cycle N, DMS Demethylation of DMSP?Note single bacteria compartment. But different bacteria cycle N, DMS Demethylation of DMSP?

35. We are starting from a position of strength with NPZD modelling. Build incrementally on it. I am not against including complexity in models, but we should build it up gradually, testing submodels rigorously at every stage. I find it surprising that some of the most complex models are going straight into GCMs. We are starting from a position of strength with NPZD modelling. Build incrementally on it. I am not against including complexity in models, but we should build it up gradually, testing submodels rigorously at every stage. I find it surprising that some of the most complex models are going straight into GCMs.

36. I�m not against PFT modelling, but we need a healthy dose of scepticism. I�m not against PFT modelling, but we need a healthy dose of scepticism.