A high-resolution coupled atmosphere-ocean model of the Great Barrier Reef: ACCESS-EMS-GBR v1.0

Abstract. We present a new regional coupled atmosphere and ocean model of the Great Barrier Reef (GBR), Australia, called ACCESS-EMS-GBR. The model comprises a regional configuration of the Australian Community Climate and Earth System Simulator (ACCESS) atmospheric model (the United Kingdom Met Office Unified Model), coupled to the Commonwealth Scientific and Industrial Research Organisation Environmental Modelling Suite (EMS) hydrodynamic and biogeochemical model of the GBR. The model includes detailed aerosol and cloud microphysics in the atmosphere, as well as hydrodynamics, biogeochemistry, ecology and coral reef processes in the ocean. When coupled, the models form a valuable tool for simulating interactions between the atmosphere and ocean. The ACCESS-EMS-GBR model was developed to assess the plausibility and implications of marine cloud brightening (MCB) in the GBR, as part of the Reef Restoration and Adaptation Program (RRAP) Cooling and Shading Sub-program (RRAP-CS) but can also be utilised to study various processes including sources of marine aerosol and the impact of aerosol deposition on marine biogeochemistry. Here, we describe the model as configured for the GBR region, including the coupling framework, and evaluate the model skill in simulating measured aerosol and seawater temperature and irradiance. We configure the model aerosol scheme and emission sources to capture observed aerosol properties over the GBR region, with boundary layer nucleation and terrestrial biogenic emissions having a large influence on aerosol number concentration, size distribution and composition. The distribution of sea salt emissions is also expanded to include the soluble Aitken mode; a significant improvement in capability for simulating MCB and possibly for improving global climate model biases.