A new era of extreme weather events in the Arctic

The Arctic has been observed to warm about three to four times faster than the global average. This rapid warming is also expected to change the frequency and severity of extreme weather events in the region. A new study published in the prestigious scientific journal Science Advances is the first to comprehensively examine long-term changes in several so-called bioclimatic variables. Bioclimate refers to climate conditions relevant to living organisms. The researchers investigated changes spanning more than seven decades, focusing especially on short-lived extreme weather events.

“Seasonality, such as the growing season and snow conditions, is known to be crucial for ecosystem functioning and the success of northern species. However, changes in bioclimatic extreme events have not been previously studied in a comprehensive way,” says research professor Juha Aalto from the Finnish Meteorological Institute.

In addition to rising average temperatures, Arctic terrestrial ecosystems are increasingly experiencing a range of extreme weather events, such as prolonged heatwaves, frost during the growing season, and warm winter spells. The extent and intensity of these changes vary across different parts of the Arctic.

Arctic regions face unprecedented climate conditions

The study shows that in many areas, some of the examined extreme weather events have only begun to appear in the past few decades. One example is rain-on-snow events. The researchers identified new regions affected by rain-on-snow events covering more than 10% of the Arctic land area. Rain falling onto snow creates particular challenges for mammals, as it promotes the formation of ice layers within the snowpack. For example, reindeer are then unable to access the lichens they rely on in their winter grazing grounds.

When looking at multiple types of extreme events together, the researchers found that at least one new extreme event has begun to occur across ca. one-third of the Arctic land area.

“This finding suggests that as the climate changes, Arctic ecosystems will be increasingly exposed to climate conditions they have never experienced before,” says Professor Miska Luoto from the University of Helsinki. “This may have significant long-term consequences for Arctic nature.”

The study also identified regions, so called hotspots, where changes in both seasonal conditions and extreme events have been especially strong. Such areas are found particularly in western Scandinavia, the Canadian Arctic Archipelago, and central Siberia.

An improved picture of northern bioclimate change

The research used modern atmospheric reanalysis data, from which the bioclimatic variables were calculated. Reanalysis combines observations with a weather model, providing the best possible information on atmospheric and surface conditions. This is particularly valuable in remote regions where direct measurements are sparse, such as large parts of the Arctic.

Accurate, up-to-date information on bioclimate is needed for monitoring and predicting Arctic biodiversity, as well as to support climate change adaptation in societies.

The international study, led by the Finnish Meteorological Institute, involved researchers from the Universities of Helsinki and Jyväskylä, as well as from the United Kingdom and France.

Reference:

Aalto, J., Kämäräinen, M., Rantanen, M., Niittynen, P., Phoenix, G., Lenoir, L., Maclean, I., Luoto, M. (2025). A new era of bioclimatic extremes in the terrestrial Arctic. Science Advances. In press.

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