Wednesday, May 5, 2021, 11:00 am — Videoconference / Virtual Event (see link below)
The Amazon and equatorial North Atlantic Ocean are nutrient-depleted ecosystems that rely on long-range transported aerosols to maintain primary productivity. African dust is believed to provide iron (Fe) and phosphorus (P) to these ecosystems, which leads to the sequestration of carbon dioxide. However, there are few measurements of African dust in South America that can robustly quantify the amount and solubility of nutrients associated with long-range transported aerosols. Additionally, the transport of supermicron and super-coarse mode aerosols, which can deposit more nutrient mass than smaller particles, is routinely underestimated due to poorly constrained physical properties. In this presentation, I will present both single-particle measurements that were used to identify a possible mechanism for the efficient long-range transport of super-coarse mode particles as well as bulk phosphorus measurements used to quantify P deposition to the Amazon and global oceans. Our results show that particle asphericity and low density increase the residence time of particles in the atmosphere, which increases the likelihood of atmospheric reactions between dust and trace species that can elevate nutrient solubility, and in the upper water column. Our measurements of bulk phosphorus confirm that North African dust transport supplies the majority of the P to the Amazon. Contrary to prior thought, we show that African biomass burning aerosol is responsible for up to half of the soluble P deposition to the Amazon. Using a chemical transport model that African biomass burning aerosols supply up to 70% of the soluble P deposited to the Southern Ocean during boreal Fall. Together, our results further elucidate the impacts of African aerosols on marine and terrestrial biogeochemical cycles.
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Hosted by: Ernie Lewis
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