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Winter warming and rain extreme events pose overlooked threat to Arctic life

Mongabay

Friday 2.5.2025

    • Accelerated Arctic warming is reshaping the polar environment, but focusing only on the impacts of long-term annual temperature rise can miss key consequences of shorter-lived, but extreme, weather shifts coming as a result of climate change.
    • A new meta-analysis highlights how extreme weather events in winter, such as rain-on-snow and temperature spikes, are increasing across the Arctic — though not every region gets the same extreme whiplash weather.
    • Even short surges of wild winter weather — 24 hours of rainfall on snow-covered ground, for example — can decimate animal and plant populations and change an ecosystem for generations. One such rain-on-snow event in 2023 killed nearly 20,000 musk oxen in the Canadian Arctic.
    • Better understanding of Arctic winter weather extremes (along with their immediate and long-term effects on flora and fauna), and factoring these into climate models, could help create more accurate, effective, region-specific conservation plans.

    It’s well established that the slow incremental “press” of rising temperatures is changing the Arctic landscape, threatening the survival of plants and animals adapted to this unique ecosystem. Less noted are short-lived “pulses” of extreme weather — another product of climate change — which can wreak long-term havoc on cold-climate-adapted wildlife and vegetation.

    These were once considered rare events, but a new study shows that unexpected warm spells and rainfall during Arctic winters are increasing. Despite the short length of these extreme weather events, the damaging effects on polar biota can be severe and lasting, according to researchers.

    The scientists suggest better tracking of such events, and the collection of more data from remote areas, and from a broader range of species, to create region-specific conservation strategies to better serve a polar biome in the crosshairs of climate change.

    “These combinations of press and pulse mean that more and more often these extreme events are crossing the physiological boundaries of species that are local to these regions,” said Maya Lemaire, lead study author and a biologist at the University of Oxford, U.K., when the paper was produced. “These regions will get pushed beyond the point where they can never recover.”

    Yearly detected individual rain-on-snow events across four Arctic regions since 1950. Total rainfall (in millimeters) for each event is represented on the y-axis, with color indicating intensity, and size of dot representing event length. Regions from top to bottom: northern Alaska, northern Fennoscandia, Svalbard, and Yamal.
    Yearly detected individual rain-on-snow events across four Arctic regions since 1950. Total rainfall (in millimeters) for each event is represented on the y-axis, with color indicating intensity, and size of dot representing event length. Regions from top to bottom: northern Alaska, northern Fennoscandia, Svalbard, and Yamal. Image by Lemaire et al., 2025 (CC BY 4-0).

    The wild side of winter

    The two-part study first analyzed decades of Arctic climate data with a focus on two kinds of extreme winter events: sudden surges in warmer temperatures, and rain-on-snow (ROS) events that occur when rain falls on snow-covered ground, floods, and then refreezes.

    Overall, the data showed these warm spikes are increasing across the entire Arctic. But the regional variability in the rain-on-snow patterns was the most interesting finding, said Lemaire: “When we came into this [research] we just assumed that rain-on-snow was getting worse everywhere. It’s not.”

    Although they analyzed data across the Arctic, four regions were of particular interest based on extreme weather impacts on biota: northern Alaska, northern Fennoscandia (Finland, Sweden, Norway and parts of Russia), the Svalbard Archipelago, and Yamal (northwestern Siberia). While all four regions showed increasing winter warming, Yamal had the highest mean temperature increase of 7.2° Celsius (13° Fahrenheit) and northern Alaska had the lowest mean increase of 2.9°C (5.2°F). For ROS events, Svalbard saw the largest increase, while northern Fennoscandia had a decrease.

    Lemaire noted that the reduction in ROS events, despite Arctic-wide increases in precipitation, is in keeping with more rainfall and less snow on the ground with rising average temperatures.

    Time series shows how a single rain-on-snow event in 1993-94 led to a significant ecosystem trophic chain reaction (related to impacts on the food web and a succession of mammals) that began with a peak in reindeer mortality (1993-1994), a subsequent reduction in Arctic fox abundance (1996 and beyond), leading to a shift in goose production and abundance (1996 and beyond). The red line indicates the ROS event-caused crash in population. Image by Layton-Matthews et al., 2023 (CC BY 4-0).
    Time series shows how a single rain-on-snow event in 1993-94 led to a significant ecosystem trophic chain reaction (related to impacts on the food web and a succession of mammals) that began with a peak in reindeer mortality (1993-1994), a subsequent reduction in Arctic fox abundance (1996 and beyond), leading to a shift in goose production and abundance (1996 and beyond). The red line indicates the ROS event-caused crash in population. Image by Layton-Matthews et al., 2023 (CC BY 4-0).

    Wildlife and plants at risk

    Unsurprisingly, extreme weather events in winter do not bode well for Arctic biota. Lemaire’s meta-analysis of 17 studies, which included 49 species, revealed that temperature spikes and ROS events were both associated with harmful impacts on Arctic life. But not all species were equally affected. The most sensitive species were vertebrates (including mammals and birds) and flowering plants.

    “The Arctic is defined by snow, and so much of the Arctic is tied into the biota, whether it’s animal or plant,” said geographer Mark Serezze, lead for the Arctic Rain On Snow Project, and director of the U.S. National Snow and Ice Data Center, who was not involved in the new research.

    “If you’re changing the snow, then you’re changing the precipitation,” he said. “This is going to impact everything.”

    Rain on snow infographic
    Rain on snow infographic Arctic rain-on-snow process and impacts. Image by Serreze et al., 2021 (CC BY 4-0).

    Some of the most destructive recorded ROS events occurred on Russia’s Yamal Peninsula in November 2007 and 2013. In both years, warmth and sudden rainfall caused an icy shield to form atop the snow, leaving tens of thousands of reindeer (Rangifer tarandus) to starve because they couldn’t get to the lichens and grasses underneath. A similar ROS-driven die-off occurred in October 2023, killing nearly 20,000 musk oxen (Ovibos moschatus) in the Canadian Arctic. In some ROS events, musk oxen have been immobilized and starved to death due to their feet being entrapped in ice.

    Regarding vegetation, winter extremes can lead to the “browning” of Arctic landscapes. ROS can harm plants by exposing them to harsh conditions, then freezing them in ice. Plants may also suffer from “frost drought,” when their roots can’t use water locked up in frozen soil. Such conditions killed up to 50% of the shoots of Arctic bell-heather (Cassiope tetragona), and mountain avens (Dryas octopetala) during a harsh Svalbard winter in 2011-2012. The following winter, a series of wild temperature swings in Arctic Norway killed 38-63% of heather shoots (Calluna vulgaris), reported one study.

    Extreme events can affect an entire ecosystem for generations to come, while also negatively impacting Indigenous communities whose livelihoods and food supply are often inextricably linked with the Arctic environment.

    A pair of two-year-old muskoxen. In October 2023, an ROS event on Banks Island, the westernmost of Canada’s Arctic islands, killed close to 20,000 musk oxen, about 25% of the herd. Like much of the remote Arctic, there were no weather stations in the area to record the event. Scientists learned about the herd loss from local hunter reports, said Mark Serreze, director of the National Snow and Ice Data Center.
    A pair of two-year-old muskoxen. In October 2023, an ROS event on Banks Island, the westernmost of Canada’s Arctic islands, killed close to 20,000 musk oxen, about 25% of the herd. Like much of the remote Arctic, there were no weather stations in the area to record the event. Scientists learned about the herd loss from local hunter reports, said Mark Serreze, director of the National Snow and Ice Data Center. Image courtesy of Joel Berger/Wildlife Conservation Society.

    A cold spot for conservation

    As the Arctic continues warming at an accelerated rate, extreme weather events will escalate and intensify, too. Noting the outsized impact of these abrupt winter weather swings, Lemaire emphasized the need to integrate them into climate models and conservation plans.

    The new meta-analysis revealed large gaps in data and knowledge, and exposed the need to build up a broader base of studies on a wider range of species. But doing a detailed regional analysis of polar extreme weather events and biota impacts in the dead of Arctic winter offers extreme challenges.

    First, it’s difficult to get robust data from remote polar regions where much of winter is draped in darkness 24/7, and where temperatures can plummet below -50°C (-58°F). In addition, it will be difficult to parse the nuanced and interconnected impacts of climate change impacts on plants and animals, said Lemaire.

    “I know we can’t research everything,“ she said. “But we need to know more to understand which areas across the Arctic are most vulnerable to being completely changed by one of these extreme events.”

    Banner image: Reindeer are iconic Arctic animals adapted to thrive in extreme cold, but new extreme winter weather conditions, including higher temperatures and rain-on-snow events, are challenging for plants and animals living in polar and subpolar ecosystems. Image by Per Harald Olsen via Wikimedia Commons (CC BY-SA 3.0).

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    Citations:
    Stroeve, J. C., Notz, D., Dawson, J., Schuur, E. a. G., Dahl-Jensen, D., & Giesse, C. (2025). Disappearing landscapes: The Arctic at +2.7°C global warming. Science, 387(6734), 616-621. doi:10.1126/science.ads1549

    Lemaire, M., Bokhorst, S., Witheford, A., Macias-Fauria, M., & Salguero-Gomez, R. (2025). Increases in Arctic extreme climatic events are linked to negative fitness effects on the local biota. Global Change Biology, 31(4), e70157. doi:10.1111/gcb.70157

    Serreze, M. C., Gustafson, J., Barrett, A. P., Druckenmiller, M. L., Fox, S., Voveris, J., … Bartsch, A. (2021). Arctic rain on snow events: Bridging observations to understand environmental and livelihood impacts. Environmental Research Letters, 16(10), 105009. doi:10.1088/1748-9326/ac269b

    Layton-Matthews, K., Vriend, S. J., Grøtan, V., Loonen, M. J., Sæther, B., Fuglei, E., & Hansen, B. B. (2023). Extreme events, trophic chain reactions, and shifts in phenotypic selection. Scientific Reports, 13(1). doi:10.1038/s41598-023-41940-6

    Bjerke, J. W., Treharne, R., Vikhamar-Schuler, D., Karlsen, S. R., Ravolainen, V., Bokhorst, S., … Tømmervik, H. (2017). Understanding the drivers of extensive plant damage in boreal and Arctic ecosystems: Insights from field surveys in the aftermath of damage. Science of The Total Environment, 599-600, 1965-1976. doi:10.1016/j.scitotenv.2017.05.050
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    Forbes, B. C., Kumpula, T., Meschtyb, N., Laptander, R., Macias-Fauria, M., Zetterberg, P., . . . Bartsch, A. (2016). Sea ice, rain-on-snow and tundra reindeer nomadism in Arctic Russia. Biology Letters, 12(11), 20160466. doi:10.1098/rsbl.2016.0466

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