RADIv2: an adaptable and versatile diagenetic model for coastal and open-ocean sediments

Abstract. Ocean biogeochemistry is being altered by anthropogenic processes such as warming, acidification, eutrophication, and deoxygenation. Global-ocean biogeochemistry models are essential for investigating present and projecting future conditions, yet they often lack detailed representations of seafloor processes, despite the seafloor’s important role in material exchange between the biosphere and geosphere. To improve the representation of exchange across the sediment-water interface, we present RADIv2, a flexible and computationally efficient diagenetic model designed to simulate benthic biogeochemical processes across a range of marine environments, from coastal zones to abyssal plains. RADIv2 incorporates key features such as benthic methane cycling, a hydrodynamically controlled diffusive boundary layer thickness and porewater dispersion to the original RADI model, which enhance its ability to capture sediment-water exchange under varied environmental conditions. Using RADIv2, we develop and validate a regression-based metamodel that predicts benthic solute fluxes (oxygen, dissolved inorganic carbon, and alkalinity). This metamodel provides a universal and computationally efficient alternative to full-complexity coupled water column-sediment biogeochemical models at the global scale. Ultimately, this approach improves the representation of global biogeochemical cycles in ocean models by improving the parameterization of sediment-water exchange.