AEROSOL GROUP
DODO Science
The Sahara is the most important source of desert dust on a global scale. Dust outbreaks from the Saharan region over the Atlantic Ocean are frequent, with intense outbreaks over western Africa having a periodicity of 5-10 days and sometimes reaching as far as the Americas.
These outbreaks impact on atmospheric composition, dynamics and provide a significant local and regional climate forcing. In addition, dust is deposited to the Atlantic ocean through dry and wet deposition which provides a source of Iron to the Ocean.
Dust in Biogeochemical Cycles
Dust outbreaks supply the ocean with nutrients, in particular, iron. This allows the fixation of nitrogen, supplying surface phytoplankton in subtropical gyres with nutrients (in otherwise nutrient starved regions), and creating a connection with the carbon cycle.
Saharan dust provides 48% of the global Fe flux to the oceans, with deposition occurring in the North Atlantic.
Dust deposition to the Atlantic Ocean is of fundamental importance to the climate system through the impacts on biological productivity and subsequently the global carbon cycle.
This process is not well constrained and depends on the dust source and composition.
In order to know and model the deposition of mineral dust into the ocean, it is crucial to know more about the atmospheric dust transport and composition from the African coast.
Dust in the Atmosphere
The strength and resulting impact of dust outflow from Africa is dependent on season.
Maximum dust transport from the Saharan region to the Atlantic moves from around 5N during the northern hemisphere winter, to 20N in summer, being driven by the seasonal migration of the ITCZ. The vertical profile also varies, being close to the surface during winter, and higher up within the Saharan Air Layer (1.5-6km) during summer.
Along with spatial and temporal vertical and horizontal variations in the dust plume, the characteristics of the dust will vary within the dust plumes. Direct aircraft measurements of microphysical and chemical properties from DODO will help to characterise these variations.