Sources of Southern Hemisphere Marine Aerosols: Insights From Carbonaceous Fraction Concentration and Stable Carbon Isotope Analysis

Abstract

AbstractMarine carbonaceous aerosols, originating from marine and continental sources, are significant global aerosol components. The understanding of marine carbonaceous aerosols is currently limited, especially in the Southern Hemisphere. Furthermore, there is an ongoing debate regarding the contributions of marine fresh and ancient carbon to marine aerosols. To address these gaps, we conducted an extensive investigation utilizing a long‐term data set of aerosol samples collected during six Antarctic cruises (28°N–78°S) from 2013 to 2020. Our analysis revealed an average organic carbon (OC) concentration of 1.29 ± 1.15 μg/m3 and an element carbon (EC) concentration of 0.13 ± 0.18 μg/m3 in the samples. These concentrations varied within a range spanning from background marine samples to those impacted by substantial continental transport. Fossil fuel combustion remained the primary source of continental influence in the marine environment, as evidenced by the OC/EC ratio. The δ13CTC value for all samples range from −22.3‰ to −28.4‰, with a mean value of −26.3 ‰. Using a three‐endmember isotopic source model, we find that continental carbonaceous aerosols make substantial contributions in the Eastern Indian Ocean (81 ± 4%), while their prevalence is lower in the Southern Ocean (SO) (44 ± 20%). In contrast to mid‐latitudes, primary marine aerosol of the SO exhibits a significantly higher contribution from the fresh carbon pool (52 ± 19%). Furthermore, our study suggests that SO sea ice may play a potential role in driving emissions from the fresh carbon pool. These findings contribute to a comprehensive understanding of the effects of carbonaceous aerosols on climate change and the ocean‐atmosphere carbon cycle.