For each short-lived trace gas of interest (e.g. DMS, CHBr3, CH3I, MeNO2, isoprene, methanol), WG 1 will:
- Compile existing databases of relevant parameters into a framework to produce the definitive dataset of air–sea fluxes. The database is comprised of sea and air concentrations which can be combined with a gas transfer velocity to produce a flux estimate. This will allow the product to be updated to reflect progress in our understanding of transfer processes and concentration fields.
- Identify issues relating to calibration of different measurements, and develop and seek funding for intercomparison experiments where STSMs will not suffice.
- Examine the data products and compare them with modelling results.
- Depending on the skill of available models, the WG will include model results and global averages in the database.
- Identify gaps in the current data set and coordinate further research to address these.
WG1 compares and synthesises our understanding of the biological and chemical processes that regulate the concentrations of these gases in seawater, with particular emphasis on the effect of atmospheric inputs on these processes. To do this it requires collaboration with WG2 to develop estimates of atmospheric inputs to the ocean.
A compilation of data on the oceanic cycling of sulphur allows for an evaluation of the different models currently in use. A model intercomparison will be conducted and the outputs synthesised for a best estimate of ocean sulphur cycling. Oceanic DMS concentrations will be converted to air–sea fluxes using the gas transfer velocities developed by WG2. Once combined with a compilation of atmospheric measurements of the oxidation products of DMS, our knowledge of the oxidation pathways and branching ratios will be evaluated and best estimates for inputs to chemistry transport models provided. This work will allow sulphur cycling in coupled general circulation models (GCMs). A vital task of WG1 is to develop a dialogue between process modellers and those implementing diagnostic models within GCMs. For other short-lived trace gases, process models need to be developed and tested against data, global fluxes estimated and their importance to atmospheric chemistry evaluated.
Products:
- Global database of trace gas concentrations in the ocean and atmosphere (DMS, CHBr3, CH3I, MeNO2, isoprene, methanol, etc.).
- Database of concentrations of oxidation products of DMS.
- Intercomparison of process and diagnostic models of air–sea sulphur cycling.
- Framework for modelling the air–sea flux of the other trace gases.
- Database of measurements of trace metals, nutrients and organics in marine aerosol.
- Database of all oceanic iron fertilisation experiments conducted to date. This information includes indicators of biological and trace gas response.