The Great Barrier Reef (GBR) has experienced five mass coral bleaching events since 2016, with adverse impacts on the coral reef ecosystem. Regional marine cloud brightening has been proposed as an intervention to reduce light and temperature in the GBR to prevent coral bleaching. Such interventions, when combined with efforts to tackle the drivers of climate change, may delay impacts and allow time for natural and assisted adaptation efforts to take effect.
Using a regional atmospheric model, we assess the impacts of injecting sea spray aerosol for marine cloud brightening in the GBR during the 2022 coral bleaching event. Impacts varied with emitted sea spray mass and particle size, with the greatest increase in aerosol and cloud droplet number concentration and subsequent reduction in surface short-wave radiation (SWR) occurring in response to emitting smaller sized particles. Emitting 1570 tonnes day-1 increased average summer low-level cloud albedo by 11% and reduced SWR by 3.5%.
The findings suggest that regional marine cloud brightening can be achieved without widespread impacts to aerosol and cloud processes beyond north-eastern Australia. Further work will investigate potential risks and explore whether the reduction in SWR could prevent or reduce the severity of coral bleaching.