Measurement report: Aerosol and cloud nuclei properties along the Central and Northern Great Barrier Reef - impact of continental emissions

Abstract

The frequency of coral bleaching events increased during the past decade in the Great Barrier Reef (GBR) due to climate change, and rising ocean temperatures. Recent work has demonstrated that enhancing local-scale cloud albedo can reduce the sea surface temperatures (SSTs) in this region. However, little research has been done on variations in the aerosol properties, as well as aerosol-radiation and aerosol-cloud interactions over different regions of the GBR, which is critical for predicting the potential for marine cloud brightening (MCB) climate forcing on a local or regional scale. Here, we examined trends in the aerosol population in terms of their physical and cloud condensation nuclei (CCN) properties during a research cruise in the Central and Northern GBR. Overall higher particle number concentrations, CCN number concentrations, and CCN activation ratios were observed during periods where the air masses passed over the continent prior to reaching the research vessel, despite lower hygroscopicity parameters. We suggest that organics contribute considerably to CCN number concentrations in this region of the GBR, which highlight the important role of additional emissions from inland Queensland. As well as the total aerosol number concentration, precipitation history along the back trajectory affected CCN number concentrations. These results represent a first step towards building a climatological understanding of aerosol and CCN properties over the GBR during summertime, a region and season where no observations have been previously reported.