Solid aerosols found in Arctic atmosphere could impact cloud formation and climate

Less sea ice and more open water means more gas and aerosol emissions from the ocean into the air, making it cloudier.

Rachel Kirpes, a graduate student at the University of Michigan, discovered that aerosolized ammonium sulfate particles did not look like typical liquid aerosols.

Kirpes and Andrew Ault discovered that the particles were solid. The results are published in the National Academy of Sciences.

Solid aerosols can change the way clouds form. As the Arctic loses ice, researchers expect to see more of these unique particles formed from oceanic emissions combined with ammonia from birds, which will impact cloud formation and climate. Understanding the characteristics of aerosols in the atmosphere is important for improving the ability of climate models to predict future climate.

The world's temperature is warming faster in the north than in the south. As we have more emissions from open water in the atmosphere, these types of particles could become more important.

Sometimes you get surprises when you make measurements, with so few observations. These particles were not like anything we had seen in the literature or anywhere else in the world.

The aerosols were 300 times smaller than a human hair and up to 400 nanometers. Ault says that aerosols are usually assumed to be liquid.

The particle becomes liquid when the relative humidity of the atmosphere reaches 80%. When you dry the aerosol out, it doesn't turn into a solid until the relative humidity is at least 40%. Researchers expect to see liquid aerosols in the air over the ocean.

We saw a new phenomenon where a small particle collides with our droplets when it is above 40% humidity. Ault said that this provides a surface for the aerosol to solidify and become a solid at a higher relative humidity than you would have expected.

The particles were more like marbles than droplets. In a region where there hasn't been a lot of measurement, those particles can end up acting as the seeds of clouds or have reactions on them.

Climate change can be impacted by the size, composition and phase of atmospheric aerosols.

Modelers need more information as events on the ground change, and that is why we help them refine their models.

Utqia is the northernmost point of Alaska and was collected in August and September of 2015. The multistage impactor is a device that has several stages that collect particles according to their size. The particles were analyzed in Ault's lab using techniques that can look at the composition and phase of particles less than 100 nanometers in size.

We wouldn't be observing these particles if there was ice near the shore. We are observing the consequences of the climate already changing, and we need to have realistic models to understand the energy budget of the atmosphere.

More information: Rachel M. Kirpes et al, Solid organic-coated ammonium sulfate particles at high relative humidity in the summertime Arctic atmosphere, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2104496119 Journal information: Proceedings of the National Academy of Sciences Citation: Solid aerosols found in Arctic atmosphere could impact cloud formation and climate (2022, March 28) retrieved 28 March 2022 from https://phys.org/news/2022-03-solid-aerosols-arctic-atmosphere-impact.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.