Arctic’s winter is changing due to recurrent warming, causing fundamental shift in the season: Scientists

Svalbard, an archipelago in the northernmost Arctic, is experiencing a fundamental shift in its winters due to recurrent warm temperatures, according to a new article published in the journal Nature Communications.

The average air temperatures in February 2025 in Ny-Ålesund, situated in northwest Svalbard and around 1,200 km from the North Pole, was -3.3 °C — considerably higher than the 1961-2001 and reached a maximum of 4.7 °C, researchers from Europe wrote. Furter, the 2025 Arctic winter air temperatures were among the warmest ever recorded.

The region saw air temperatures higher than 0°C on 14 of the 28 days of February 2025. Such sustained warmth, along with prolonged rainfall, triggered widespread melting of snow and ice. “These were sustained thaw conditions in the middle of winter, not a brief spike in temperature. That’s what makes this event so concerning,” James Bradley, reader in environmental science at Queen Mary University of London, and the author of the study, told Down To Earth.

“What we are seeing is a transformation of the Arctic winter. It’s not just getting warmer — it’s crossing thresholds that fundamentally change how the season behaves. The presence of rain instead of snow, thawed soils instead of frozen ground and meltwater ponds in mid-winter all point to a season in transition,” Bradley explained.

The study also showed that the episodic warming of February 2025 was not an isolated occurrence, but a recurring phenomenon in recent decades due to human-induced climate change. The researchers expect to see an increase in the frequency and magnitude of winter warming episodes, with climate change impacting Arctic systems and societies.

The Arctic is warming fastest in winter because of feedbacks linked to physical processes, including sea ice loss, increased cloud cover and changes in heat transport, Bradley explained. He added that when sea ice retreats in summer, the ocean absorbs more heat. In winter, that heat is released back into the atmosphere, especially in areas that would normally be ice-covered. 

“Warmer air and more moisture also lead to increased cloud cover, which traps longwave radiation and keeps surface temperatures higher. This makes winter particularly vulnerable to warming. Svalbard is one of the fastest-warming places in the Arctic,” the expert highlighted.

Svalbard is warming at six to seven times the global average rate, with the winter temperatures over the archipelago rising at nearly twice the annual average. The annual precipitation in west Svalbard is increasing 3-4 per cent per decade, most of which is falling as rain.

The researchers travelled to Ny-Ålesund to study glacial and terrestrial microbial communities and their role in carbon and other elemental cycles during the dark, frozen, winter period.

The team was expecting sub-zero temperatures and extensive snow cover, conditions typical to Svalbard during winter. During their visit in February 2025, the team encountered air temperatures persistently above 0 °C, as well as rainfall and exceptionally low snow cover.

They also observed meltwater pooling above frozen ground in tundra — treeless regions found in the Arctic. These pools formed vast temporary lakes, glacier-fed streams and rivers, which are expected to remain frozen until springtime.

Snow cover on the tundra was reduced to zero across large areas and vegetation emerged through the melting snow and ice. The winter experienced by the team was characterised by green hues that are typically associated with spring and summer.

Further, the uppermost soils of the active layer of permafrost — any ground that remains completely frozen for at least two consecutive layers — were free of snow in multiple areas, further altering the terrain's stability.

Low elevations saw drastic changes with warm temperatures and rainfall on nearby glaciers diminishing snow accumulation. The researchers saw multiple ice layers in the remaining snowpack, which indicated that February’s melting event was not a one-off occurrence this winter.

In their article the scientists warned of lasting environmental impacts. For example, when meltwater enters the soil and saturates the pore spaces with water, it then refreezes into ice. 

Such icings restrict the infiltration of water produced by snowmelt, resulting in meltwater pools over the frozen ground. This standing water refreezes, producing a thick icy crust over the tundra.

The problem is that these impermeable crusts block gas exchange between the soil and the atmosphere, potentially limiting oxygen availability in the soil, impacting microbes and increasing methane production.  

Persistent thick ice crusts also significantly reduce the availability of winter forage for reindeer and other herbivores, affecting animal health and survival.

Increased winter warming threaten human communities and infrastructure by increasing snowpack instability and increasing the risk of avalanches in populated and frequently travelled areas of Svalbard, the researchers warned.

This is already happening. Many buildings in Ny-Ålesund, including those housing the UK Arctic Research Station and the Dirigibile Italia Arctic station, have recently been re-supported on new foundations due to instabilities caused by thawing permafrost and a deepening active layer, the researchers wrote.

These changing winter conditions, according to the team, raised concerns about the long-term feasibility of winter research practices and logistics under increasingly variable conditions and rising temperatures in Ny-Ålesund, which has been a hub for scientific research in the high Arctic for the last five decades.

“Winter warming in the Arctic has long reached melting point and is reshaping Arctic landscapes. These winter warming events are seen by many as anomalies, but this is the new Arctic,” the researchers wrote in the paper.

The Arctic, especially Svalbard, is experiencing unprecedented winter warming, with February 2025 temperatures far exceeding historical norms. This shift, driven by climate change, results in snow and ice melting, forming impermeable crusts that disrupt soil-atmosphere gas exchange. The warming trend poses risks to wildlife, human infrastructure, and scientific research, marking a fundamental change in Arctic winter behavior.