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Tropical Rains Controlling Deposition of Saharan Dust Across the North Atlantic...

van der Does, M., G. A. Brummer, F. C. J. van Crimpen, L. F. Korte, N. M. Mahowald, U. Merkel, H. Yu, P. Zuidema, and J. W. Stuut (2020), Tropical Rains Controlling Deposition of Saharan Dust Across the North Atlantic Ocean, Geophys. Res. Lett., 47, doi:10.1029/2019GL086867.

Mineral dust plays an important role in the atmospheric radiation budget as well as in the ocean carbon cycle through fertilization and by ballasting of settling organic matter. However, observational records of open‐ocean dust deposition are sparse. Here, we present the spatial and temporal evolution of Saharan dust deposition over 2 years from marine sediment traps across the North Atlantic, directly below the core of the Saharan dust plume, with highest dust fluxes observed in summer. We combined the observed deposition fluxes with model simulations and satellite observations and argue that dust deposition in the Atlantic is predominantly controlled by summer rains. The dominant depositional pathway changes from wet deposition in summer to dry deposition in winter. Wet deposition has previously been suggested to increase the release of dust‐derived nutrients and their bioavailability, which may be a key contributor to surface‐ocean productivity in remote and oligotrophic parts of the oceans. Plain Language Summary Large quantities of dust are emitted from the Sahara Desert and blown over the (sub)tropical North Atlantic Ocean. Atmospheric dust plays an important role in the Earth's climate, but observations of open‐ocean deposition are sparse. Here, we present a continuous, 2‐year record of dust deposition across the North Atlantic Ocean, between Africa and the Caribbean. We compare and evaluate measurements of dust deposition with model simulations and satellite observations. The combined results reveal that tropical rains dominate dust deposition across the Atlantic. In particular, the rain is responsible for the high dust deposition during summer and may also affect the nutrients that are carried with the dust. Since previous studies suggest that the nutrients that reach the surface ocean with the rain are more readily available for phytoplankton productivity, the wet deposition of dust potentially has a major impact on the ocean carbon cycle.

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Research Program: 
Atmospheric Composition Modeling and Analysis Program (ACMAP)
Radiation Science Program (RSP)