The FuGas 2.1 framework for atmosphere-ocean coupling in geoscientific models: improving estimates of the solubilities and fluxes of greenhouse gases and aerosols

Abstract. Accurate estimates of the atmosphere-ocean balances and fluxes of greenhouse gases and aerosols are fundamental for geoscientific models dealing with climate change. A significant part of these fluxes occur at the coastal ocean which, although much smaller than the open ocean, is also much more heterogenic. The scientific community is becoming increasingly aware of the necessity to model the Earth at finer spatial and temporal resolutions, which also requires better descriptions of the chemical, physical and biological processes involved. The standard formulations for the gas transfer velocities and solubilities are 24 and 36 years old, respectively, and recently, new alternatives have emerged. We developed a framework congregating the geophysical processes involved which are customizable with alternative formulations with different degrees of complexity and/or different theoretical backgrounds. We propose this framework as basis for novel couplers of atmospheric and oceanographic model components. We tested it with fine resolution data from the European coastal ocean. Although the benchmark and alternative solubility formulations agreed well, their minor divergences yielded differences of many tons of greenhouse gases dissolved at the ocean surface. The transfer velocities largely mismatched their estimates, a consequence of the benchmark formulation not considering factors that were proved determinant at the coastal ocean. Climate Change research requires more comprehensive simulations of atmosphere-ocean interactions but the formulations able to do it require further calibration and validation.