Svalbard winter warming is reaching melting point
Svalbard is at the front line of the climate crisis, warming at six to seven times the global average rate1. Human-caused global warming is particularly amplified in the Arctic, causing the climate in the Arctic to warm more quickly than the rest of the Earth2. The winter period is experiencing the highest rates of warming3 with winter temperatures over Svalbard rising at nearly twice the annual average4,5,6. Meanwhile, centennial trends for annual precipitation in west Svalbard show increases of 3–4 % per decade, of which a greater proportion is falling as rain7. As such, over the past 40 years, rain-on-snow events have significantly increased, and rain is projected to become the dominant form of precipitation in the Arctic by the end of this century7.
This year, Arctic winter air temperatures were among the warmest ever recorded8. In Ny-Ålesund, the world’s northernmost permanent settlement, situated in north-west Svalbard and approximately 1,200 km from the North Pole, the air temperature average for February 2025 was -3.3 °C — considerably higher than the 1961-2001 average for this time of year of -15 °C (Fig. 1a)9, and reached a maximum of 4.7 °C. Air temperatures higher than 0 °C were recorded in Ny-Ålesund on 14 of the 28 days of February 2025 (Fig. 1b). Such sustained warmth, coupled with prolonged rainfall, triggered widespread melting of snow and ice. When winter warming crosses the 0 °C threshold, it marks more than just a warm anomaly — it signals a fundamental shift in Arctic winter dynamics. Episodic thawing events during winter can have significant and lasting environmental consequences, including influencing ice layer formation, triggering microbial activation, altering nutrient discharge, and affecting permafrost thaw and ground ice development. The episodic warming event of February 2025 was not an isolated occurrence: winter warming events in Svalbard have been a recurring phenomenon in recent decades as a consequence of anthropogenic climate change3. As climate change continues to take hold, the frequency and magnitude of winter warming episodes will increase, and so will their effects on Arctic systems and societies.
a Surface air temperature anomaly for February 2025 over the Arctic region relative to the February average for the period 1991–2020. Data source: ERA58, obtained from the Copernicus Climate Change Service (C3S), implemented by the European Center for Medium-Range Weather Forecasts (ECMWF)24. b Daily air temperatures for February 2025 from Ny-Ålesund observation station, Svalbard, elevation 8 m, established in July 1974. The solid black line is the daily average. The black boxes represent the minimum and maximum temperatures recorded. The horizontal dashed black line represents the average air temperatures for Longyearbyen, Svalbard, for the month of February between 1959–2001, estimated from the instrumental Svalbard Airport series9. Background stripes are colored according to the daily maximum temperature.
Our teams are working in Ny-Ålesund to study glacial and terrestrial microbial communities and their role in carbon and other elemental cycles during the dark, frozen, winter period, for which data remains scarce10. Our winter-time field campaigns in Svalbard are conducted under the expectation of sub-zero temperatures and extensive snow cover — conditions that have historically been typical in Svalbard during winter, but in recent years are increasingly threatened by climate change. However, in February 2025, we encountered air temperatures persistently above 0 °C, as well as rainfall, exceptionally low snow cover, and pooling meltwater covering the tundra. Wintertime warming and rain turned Ny-Ålesund and the surrounding landscape into a melting ice rink, disrupting planned sampling efforts, forcing adaptations in methodologies, provoking new scientific questions, and raising concerns about the long-term feasibility of our winter research practices and logistics under increasingly variable conditions and rising temperatures.