Dust

Every year, numerous dust storms take place and in total about 180 million tons of so-called mineral dust are blown out from the northwest African deserts (including Sahara and Sahel) westward across the Atlantic Ocean. Calculations and recent satellite measurements by NASA have demonstrated that between Africa and the Caribbean, about 140 Million Tons of mineral dust are deposited on the ocean. Besides that, millions of tons are deposited on the South American rainforest. Such amounts of dust deposited over such a large area are likely to have an impact.

Dust storm Godzilla in June 2020 is an example of how large amounts of dust are blown across the Ocean (copyright: NASA):

Research has shown that desert dust influences the Earth's climate in various ways:

- It reflects solar energy through fine-grained dust in the upper atmosphere. This prevents the heat from reaching the Earth, which has a cooling effect.
- Slightly larger dust particles floating around in the lower atmosphere actually have a warming effect. They absorb solar energy that is reflected by the Earth's surface and was actually on its way back into space. In this way, they act as a greenhouse gas.
- Desert dust as food for plankton in the ocean promotes the storage of CO₂ by plankton.
- We have recently demonstrated that dust can also play a role in the removal of an even more harmful greenhouse gas: methane (CH₄).

We would like to know exactly how the relationships between desert dust and plankton in the ocean work and whether it might even be possible to artificially supply the ocean with nutrients from desert dust as climate mitigation strategy.

In two affiliated projects at NIOZ and another one at partner institute MARUM-Bremen we have studied Saharan dust by collecting it with instruments that we placed underneath the dust plume. In 2012 we deployed tethered buoys with autonomous dust collectors, powered by solar panels, which pump air through filters. 

In addition, we placed moorings with sediment traps to collect material settling through the ocean. Both the buoys and moorings provide time series, not only of dust, but also of phytoplankton that responds to the nutrients in the dust. We then compare these data with satellite images and meteorological data.

A third way to sample deposited dust is by taking sediment cores from the ocean floor.

Since we deployed the instruments for the first time in 2012, we have re-visited them throughout the past years on expeditions with various research vessels such as RV Pelagia, but also on foreign ships such as FS Maria S Merian, FS Meteor and RRS James Cook.

The projects TRAFFIC (funded by NWO) and DUSTTRAFFIC (funded by ERC) focused on the marine-environmental effects of dust deposition. We have published some very nice results already, with more papers coming up. 

For example, we are gaining a better understanding of how wind can transport sediment over long distances. This involves sorting by grain size, shape and composition. The sorting that we observe over thousands of kilometres also appears to occur systematically over much shorter distances, along the beach and in the dunes. This also appears to have an effect on the ecology of the coastal area, for example the distribution of different plant species. Understanding these kinds of processes is very important. It could probably help us to give nature a helping hand and perhaps even restore it where possible.

Aeolian studies are also carried out on the island of Texel: a notch has been dug in the foredune, to allow sand being blown from the beach toward the grey-dune area that is suffering from acidification due to excess nitrogen deposition. This way, the calcium carbonate of the beach sands can neutralise the acid soils, the foredunes will get more solid, meanwhile storing more freshwater. In November 2023, we started a T0-study of the area. In January 2025 the notch was dug and we are monitoring the effects ever since.