Yahoo Autos Thawing permafrost is full of ice-forming particles that could get into atmosphere
The Research Brief is a short take about interesting academic work.
The big idea
Permafrost – frozen soil in the far north – is thawing, releasing greenhouse gases and long-lost microbes. But one thing that scientists have not studied extensively is whether permafrost contains certain kinds of particles that could affect clouds and weather.
As atmospheric scientists, we found in a 2021 study that thawing permafrost contains lots of microscopic ice-nucleating particles. These particles make it easier for water droplets to freeze; and if the ones in permafrost get airborne, they could affect Arctic clouds.
In the summer of 2018, one of us, Jessie Creamean, went to Fairbanks, Alaska, and collected samples of permafrost from a research tunnel deep underground. These samples ranged from 18,000 to 30,000 years old, and our team tested them to see how many ice-nucleating particles are hiding in permafrost.
It turns out permafrost contains a ton of them – up to 100 million highly active individual particles per gram of mostly dead microbes and pieces of plants. This density is on par with what is found in fertile soils, which are some of the most concentrated sources of ice-nucleating particles on Earth. Everywhere in the world, ice-nucleating particles typically play a major role in cloud behavior, and the strength of that effect is still being studied.
Why it matters
No one yet knows whether ice-nucleating particles from permafrost are getting into the atmosphere and affecting clouds. But the theory of how ice-nucleating particles change clouds is understood.
Clouds are made up of billions of tiny water droplets or ice crystals, often a mix of both. A cloud is like a forest of trees: All water droplets of the cloud require a seed – a tiny aerosol particle – to form and grow on. Almost any little speck of material from the land or the ocean can be the seed of a liquid cloud droplet. Because of their unique ability to line up water molecules into an icelike grid, they help supercooled liquid in a cloud to freeze at warmer temperatures.
Ice-nucleating particles are extremely good at forming small ice crystals – a rare skill found in less than 1 in a million of all the particles floating around in the air. Ice-nucleating particles can be mineral dust from deserts, specks of soil from farm fields or – like what we found in the permafrost – bacteria and bits of biological material from oceans or plants.
