Magnetic minerals in atmospheric Saharan dust

Atmospheric dust is an important component of the global climate system. It has large-scale effects on the planetary radiation budget, the albedo of snow/ice, and biogeochemical cycles. Despite this, particularly the magnetic minerals in atmospheric dust have been poorly described in aerosol models. The absorption effects of magnetic particles can be comparable to black carbon, they promote ice nucleation and therefore play a role in cloud formation, and they increase the input of iron into ocean ecosystems. We aim to contribute to characterizing these dust particles and their source areas, long-range transport, and scattering effects.

The research material consists of Saharan dust deposited on snow in Finland, collected as an extensive citizen science campaign by the Finnish Meteorological Institute during 2021. The first results regarding the dust samples were published by Meinander et al. (2023). The multidisciplinary study showed that the dust originated from the Sahara and the Sahel regions (south of Sahara), based on the magnetic properties of the particles, and the System for Integrated modeLling of Atmospheric coMposition (SILAM) model. The results form the basis for the present project.

A detailed magnetic characterization of the dust samples is one of the main objectives. Identifying properties such as the types and grain sizes of the magnetic particles is crucial in indicating the source area of the dust and improving the light scattering and absorption models of dust. Magnetic measurements, including initial susceptibility with two frequencies, anhysteretic remanence, and isothermal remanence, have been carried out for a set of 47 dust samples. The preliminary results are in good agreement with the previously published magnetic analyses (Meinander et al. 2023), showing signs of the presence of both Saharan and anthropogenic dust.

In the future, the scattering and absorption of light by the dust particles will be studied both experimentally and theoretically. The existing numerical methods will be extended for the treatment of magnetic particles, particularly.



Meinander, O., Kouznetsov, R., Uppstu, A. et al. African dust transport and deposition modelling verified through a citizen science campaign in Finland. Sci Rep 13, 21379 (2023). https://doi.org/10.1038/s41598-023-46321-7