It’s Science Wednesday! Back in June/July 2020, parts of the US and the Caribbean saw darker hazier skies due to large clouds of dust coming from the Sahara Desert in Africa. While the dust storm was a part of a regular meteorological phenomenon, the 2020 cloud of particulates was one of the most intense on record. Read more here from a previous Science Wednesday post.
Now, in February 2021, dust storms from the Sahara have again transported particulates – but this time northwards, towards Europe and European mountain ranges stretching from the Pyrenees to the Alps. Dust storms are important in that they can fertilize soils but they can also degrade air quality, which is not ideal for human health. Again, while events like this are not unexpected, as, a few times a year, a sufficiently strong and persistent southerly wind flow can funnel plumes of dust northward into Europe, this event was particularly intense, turning European skies more Mars-looking, with tints of orange and red.
Dark particulates falling on snow and ice in the alpine regions can accelerate melting, as was covered in last week’s Science Wednesday. A paper that was published in 2019 found that, after looking at dust deposition on high alpine snowpack these last few years, the dust does in fact reduce snow cover duration in Europe. Through a process called the snow-albedo feedback, dust darkens snow making it less reflective, which leads to increased snowmelt over time. Take a look at this research in the European Alps.
Saharan dust can also transport microorganisms into Europe. Specifically, this paper found that bacterial communities in the alpine snow of a Mont Blanc glacier were likely contaminated because of Saharan dust transport!
photo of the skies over Germany by Andrea Huber (and sent to me by Elke König).