Aerosol and seawater beryllium-7 concentrations from the French GEOTRACES GS02 SWINGS cruise aboard R/V Marion-Dufresne (MD229) from January to March 2021

Beryllium-7, a cosmogenic radioactive isotope with a half-life of 53.3 days, is formed in the atmosphere, attaches to aerosol particles, and is deposited on the earth's surface through wet and dry processes. In this project, we measured Be-7 concentrations in aerosol particles and in seawater samples (depths < 200 meters) collected on the French GEOTRACES section GS02 SWINGS cruise aboard R/V Marion-Dufresne. The cruise originated at Réunion Island on 11 January 2021 and concluded at Réunion on 8 March 2021. Nineteen aerosol samples and seawater from eleven stations in the South Indian Ocean were collected. The dataset will be used to study the deposition of trace elements and isotopes (TEIs) and upper ocean mixing processes. Aerosol deposition is an important source of TE micronutrients to open ocean areas that are far removed from riverine sources. But, while the collection aerosol of samples for TEI analysis is straightforward, estimating the deposition flux also requires an appropriate deposition velocity (i.e. deposition flux is the product of the aerosol concentration and deposition velocity). Because Be-7 is supplied to the open ocean exclusively through aerosol deposition and it is removed through radioactive decay, the water column inventory and aerosol concentration of Be-7 can be used to derive the deposition velocity applicable to aerosol TEIs.