The Arctic region is very sensitive to climate change and the ongoing changes in the Arctic are a crucial factor affecting the global climate. Therefore, it is important to understand what determines the Arctic climatic processes. With a grant from the Villum Foundation, the researchers behind the ICARUS project aim to examine how specific microorganisms can affect formation of ice in clouds.
By Nat-Tech Communication 2021
It is important that we examine and map the reasons behind climate change in the Arctic. So far, much research has focused on understanding the role of greenhouse gases in climate change. A number of researchers are now looking towards the clouds.
Tina Šantl-Temkiv, an assistant professor at the Department of Biology at Aarhus University, is one of them. She is heading the ICARUS project, which will examine microbial aerosols and their influence on the formation of clouds in the Arctic.
"The formation of clouds and processes in them depend on small particles we call aerosols. Aerosols act as seeds for the formation of the water droplets and ice particles that clouds consist of. We know that aerosols are crucial for cloud formation, but we don't know much about how specific types of biological aerosols affect the formation of clouds and ultimately the climate," she says.
To remedy this, data generated by ICARUS will be included in climate models. In this way, ICARUS will help to understand how biological aerosols affect the Arctic climate. In the longer term, better climate models can help to identify, and possibly remediate, key climate challenges.
"Ice-nucleating proteins can initiate ice formation, and ice formation is a very important part of cloud formation. For example, for most precipitation that is generated in clouds over land, first ice must form in the clouds," says Tina Šantl-Temkiv, and she continues:
"These ice particles are very good in accumulating water vapour on their surface and in this way they grow large and heavy enough to fall to the ground as precipitation."
Because of the specific structure of the ice-nucleating proteins they can initiate ice formation at higher temperatures than grains of dust. In order to understand the significance of the aerosol for ice formation, it is important to note that very clean water can be cooled to -40°C before it spontaneously freezes into ice. Pollution that can for example be in the form of dust particles increases the freezing point of water. Mineral particles such as desert dust typically make ice form at temperatures below -20°C. By comparison, ice-nucleating proteins can make ice form at temperatures just below 0°C.
"Ice-nucleating proteins make ice form at much higher temperatures than mineral particles. And even though they are less abundant in the atmosphere compared to dust, it seems that they may be important for cloud formation. This is backed-up by a growing number of studies, in which scientists either collect aerosol samples and detect ice-nucleating proteins directly in the atmosphere or they use remote sensing techniques to detect ice in clouds at high sub-zero temperatures" she says.
By forming ice in clouds, ice-nucleating proteins affect cloud optical properties. This affects the albedo of the clouds, or in other words clouds' ability to reflect sunlight back into space and thus energy away from the Earth.