The first Greenhouse Gases project

The first ESA OceanFlux Greenhouse Gases (GHG) project, led by Dr David Woolf, ran from November 2011 to January 2013

It focused primarily on interfacial transfer rates and thus upon concentrations on either side of the sea surface, and air-sea transfer coefficients.  The significance of OceanFlux GHG extends more broadly for example to the global marine cycling of carbon and the position of OceanFlux GHG in the broader context of marine carbon cycling and the related international initiatives is illustrated here :


A schematic of marine carbon cycling indicating the scope of OceanFlux GHG and of the large international programs SOLAS and IMBER

The specific focus of OceanFlux-GHG is encapsulated in the air-sea gas flux equation. The determination of the global fluxes, F, of carbon dioxide and other greenhouse gases is the primary objective and to reach that goal, the various parameters on the right-hand side of the equation must first be determined. OceanFlux-GHG spent much of its effort in the determination of the transfer velocity, k.

Transfer is primarily a result of stirring at and near the interface by the wind, but the process is complicated by wave physics generally, by breaking waves and bubbles at high wind speeds and by surfactants and convection at low wind speeds. The net flux, F, is also proportional to the concentration difference across the interface, written in the figure as the product of solubility, α, and partial pressure, p, at either side of the interface. OceanFlux-GHG depended on measurements and archiving of partial pressures external to the project. In particular, it relied on the Surface Ocean CO2 Atlas (SOCAT) to provide measurements of oceanic partial pressure of carbon dioxide. OceanFlux-GHG also devoted a large amount of resource and time to the determination of solubilities (dependent on temperature and salinity) and to the correct calculation of the concentration difference.

The first oceanFlux GHG project made a number of key advances including the development and characterisation of the first global satellite Earth observation derived air-sea CO2 climatology :


                                      Mean air-sea flux of CO2 for 2010 from the OceanFlux-GHG climatology


To achieve this, the project also developed an open-source software toolbox for calculating air-sea gas fluxes and published a number of papers on algorithm development, methods and regional studies.  More detailed information on these achievements can be found in the final project report and the published journal papers