Downward particle fluxes of biogenic matter and Saharan dust across the equatorial North Atlantic
Korte, L.F.; Brummer, G.-J. A.; van der Does, M.; Guerreiro, C.V.; Hennekam, R.; van Hateren, J.A.; Jong, D.; Munday, C.I.; Schouten, S.; Stuut, J-B W. (2017). Downward particle fluxes of biogenic matter and Saharan dust across the equatorial North Atlantic. Atmos. Chem. Phys. 17(9): 6023-6040. https://dx.doi.org/10.5194/acp-17-6023-2017
In: Atmospheric Chemistry and Physics. Copernicus Publ: Göttingen. ISSN 1680-7316; e-ISSN 1680-7324, meer
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| Auteurs | | Top |
- Korte, L.F., meer
- Brummer, G.-J. A., meer
- van der Does, M., meer
- Guerreiro, C.V.
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- Hennekam, R., meer
- van Hateren, J.A.
- Jong, D.
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| Abstract |
Massive amounts of Saharan dust are blown fromthe coast of northern Africa across the Atlantic Ocean towardsthe Americas each year. This dust has, depending onits chemistry, direct and indirect effects on global climatewhich include reflection and absorption of solar radiation aswell as transport and deposition of nutrients and metals fertilizingboth ocean and land. To determine the temporal andspatial variability of Saharan dust transport and depositionand their marine environmental effects across the equatorialNorth Atlantic Ocean, we have set up a monitoring experimentusing deep-ocean sediment traps as well as land-baseddust collectors. The sediment traps were deployed at fiveocean sites along a transatlantic transect between north-westAfrica and the Caribbean along 12? N, in a downwind extensionof the land-based dust collectors placed at 19? N on theMauritanian coast in Iouîk. In this paper, we lay out the setupof the monitoring experiment and present the particle fluxesfrom sediment trap sampling over 24 continuous and synchronizedintervals from October 2012 through to November2013. We establish the temporal distribution of the particlefluxes deposited in the Atlantic and compare chemicalcompositions with the land-based dust collectors propagatingto the downwind sediment trap sites, and with satelliteobservations of Saharan dust outbreaks.First-year results show that the total mass fluxes in theocean are highest at the sampling sites in the east and west,closest to the African continent and the Caribbean, respectively.Element ratios reveal that the lithogenic particles depositednearest to Africa are most similar in composition tothe Saharan dust collected in Iouîk. Downwind increasingAl, Fe and K contents suggest a downwind change in themineralogical composition of Saharan dust and indicate anincreasing contribution of clay minerals towards the west. Inthe westernmost Atlantic Ocean, admixture of re-suspendedclay-sized sediments advected towards the deep sedimenttrap cannot be excluded. Seasonality is most prominent nearboth continents but generally weak, with mass fluxes dominatedby calcium carbonate and clear seasonal maxima ofbiogenic silica towards the west. The monitoring experimentis now extended, with autonomous dust sampling buoys forbetter quantification of Saharan dust transport and depositionfrom source to sink and their impact on fertilization and carbonexport to the deep ocean. |
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