The Arctic’s hidden influence: How biological aerosol particles can impact food security

03 Oct 2023 --- International scientists at Stockholm University have uncovered the vital role of primary biological aerosol particles (PBAP) in ice formation within Arctic clouds. The particles – bacteria, spores, pollen, plant debris and viruses are emitted from vegetation, biological activity on snow, barren land, sea spray and dust.  

According to the scientists, the findings – published in Nature Communications – have far-reaching implications for climate science around the rapidly changing Arctic climate. The findings come on the heels of several studies showing the effects of warming in the Arctic and Antarctic climates on food and nutrition security.

“We showed the link directly using data from the Arctic, where observations are sparse. The Arctic is also the place where climate change manifests most. Our evidence will not change the way we conduct climate science in the future, it is rather another piece in the puzzle on how the climate (and especially clouds and aerosols) work in the Arctic,” Paul Zieger, associate professor at Stockholm University and co-author of the study, tells Nutrition Insight.

Arctic PBAP can be of marine or terrestrial origin or transported from lower latitudes. The particles are poorly understood because of considerable challenges in sampling and quantifying their presence exacerbated by the fact that observations are scarce in the Arctic and concentrations of PBAP are low.

“This research offers critical insights into the origin and properties of biological and ice nucleating particles in the Arctic that could enable climate model developers to improve the representation of aerosol-cloud interactions in models and reduce uncertainties related to anthropogenic radiative forcing estimates,” explains Zieger.

Opportune time for biological particlesThe tundra near the Ny-Ålesund village, a potentially major source of bioaerosols in the Arctic. The Zeppelin Observatory is in the background (Credit: Gabriel Freitas).
Increases in open ocean areas and snow-free tundra, both sources of biological particles in the Arctic, are expected in the coming decades. Gaining a deeper understanding of the relationship between these particles and clouds will provide valuable insights into the ongoing transformations at the Arctic.

Recently, scientists pointed to the “far reaching” consequences of temperature changes in the Arctic, which can amplify warming patterns throughout the ocean, which they stated increases the need for revised governance in local fisheries.

Additionally, scientists have also warned of ocean warming effects on the Atlantic Meridional Overturning Circulation, which, if stalled, could have severe implications for global food security.

“Primary biological aerosol particles, such as pollen, spores or bacteria, are known to be good nuclei to form ice crystals within clouds. Besides PBAP also other particles form ice crystals in the atmosphere (such as dust particles) but PBAP form ice at warmer temperatures than. dust,” Zieger explains. 

“So ice formation within the cloud can already happen at temperatures below 0°C. Clouds are an important part of the climate system and their phase – meaning how much ice crystals vs liquid droplets are found within the cloud – is important for the cloud’s microphysical properties (with impact on precipitation and cloud lifetime).”

Confirming Arctic acceleration
Two methods were used to retrieve cloud condensation nuclei or ice nucleating particles (INP) concentrations at the site in Svalbard, Norway. The scientists say they present strong evidence that PBAP were the main contributors to the concentration of INP active at higher air temperatures. 

The results will improve the source attribution of PBAP and INP in the Arctic and help constrain their respective representation in climate models. The research has been conducted over several years at the Zeppelin Observatory in the remote Norwegian archipelago of Svalbard, Norway, known as the High Arctic. 

“We have individually identified and counted these biological particles using a sensitive optical technique reliant on light scattering and UV-induced fluorescence. This precision is essential as we navigate through the challenge of detecting these particles in minuscule concentrations, akin to finding a needle in a haystack,” explains Gabriel Freitas, lead author of the study and Ph.D. student at Stockholm University.

Meanwhile, multiple threats are jeopardizing the global agricultural system, including crop damage, malnutrition and food insecurity, exacerbated earlier this year by wildfires in Canada. Smoke from the wildfires spread all the way to Norway, and this June was the hottest on record in some parts of the world.

Detecting sugar alcohol compounds
Paul Zieger from Stockholm University.
The presence of biological particles was found using various methodologies, including electron microscopy and the detection of specific substances, such as the sugar alcohol compounds arabitol and mannitol, indicators of fungal spores.

The study analyzed seasonal dynamics of biological particles, establishing correlations with variables such as snow cover, temperature and meteorological parameters. 

“While arabitol and mannitol are present in various microorganisms, their presence in air are related to fungal spores, and might originate both from local sources or from long range atmospheric transport,” says Karl Espen Yttri, senior scientist at the Climate and Environmental Research Institute NILU and co-author of the study.

To quantify the ice nucleating particles the researchers collected particles on filters over a week, then carried out rigorous laboratory analyses.

“Our method can quantify the ice nucleating ability of aerosol particles immersed in water droplets at temperatures ranging from 0°C down to about -30°C, thereby revealing the concentration of ambient ice nucleating particles active in Arctic low-level clouds,” says Yutaka Tobo, associate professor at the National Institute of Polar Research in Japan and co-author of the study.

The filters were subjected to additional heating at 95°C allowing the scientists to identify the proteinaceous component of ice nucleating particles which sheds light on their potential biological origin. 

By Inga de Jong