Publikasjonsdetaljer
Tidsskrift: Bulletin of The American Meteorological Society - (BAMS), vol. 107, S296–S351, 10. august 2026
Doi: doi.org/10.1175/bams-d-26-0123.1
Arkiv: hdl.handle.net/11250/5558245
Arkiv: nva.sikt.no/registration/01a015144704-2372977a-d2d8-47c0-bdde-46476d036f34
Sammendrag:
Environmental conditions across the Arctic, a vast area above 60°N, look today remarkably different than one or two decades ago. Modern satellite era measurements of Arctic annual surface air temperature (1979–2025) show that the region has, on average, warmed roughly three times faster than the rest of the planet. Human emissions of heat-trapping gases are driving the change globally with additional processes in the Arctic amplifying the heating (section 5c). The impacts touch every corner of the terrestrial and marine landscape, including serious compounding hazards for people in the Arctic. This chapter delves into these long-term trends and details 2025 observations across the Arctic system, including a section on 2023/24 observations on glaciers and ice caps outside of Greenland (section 5h, which alternates yearly with a section on Arctic river discharge).
Examining surface temperature in the Arctic, 2025 was the second warmest year since the observational record began in 1900 (section 5c). The surface temperature anomaly for the year was 1.38°C above the 1991–2020 mean, a reflection of warmer-than-usual temperatures occurring across seasons. Autumn and winter continue to show the strongest increases in surface warming as compared to global trends, and 2025 marked the 12th consecutive year that Arctic temperature anomalies were higher than global surface temperature anomalies. Temperature changes also occur from the Earth’s surface up through the troposphere and stratosphere. The Arctic troposphere has warmed 0.3°C decade−1 since 1958, while the stratosphere has cooled by a similar amount, an expected pattern with human-caused climate change (section 5b). In 2025, polar tropospheric air temperatures were the second highest on record.
Overall warming in the Arctic is accompanied by increases in precipitation, including the potential for bigger rain and snow events. During the period 1950–2025, there was an upward trend in annual precipitation totals, including significant upward trends in all seasons (section 5d). Examining annual records, 2025 had the third highest annual precipitation total on record, and the largest precipitation anomalies with respect to 1991–2020 were in winter (112%), spring (108%; the highest spring anomaly on record), and autumn (104%). Snow cover extent is connected to these coupled changes in precipitation and temperature, with patterns of snowpack buildup and melt shifting over the last several decades. In 2025, Arctic snow cover extent was roughly normal in Eurasia and North America in May but dropped below normal in June with early loss of snow cover, a now common occurrence (section 5i).
Arctic landscapes both respond to and influence temperature and precipitation changes. With vast areas of tundra as well as permafrost, the Arctic is home to a unique physical system that is responding rapidly to overall warming. Changes in Arctic tundra plants and productivity, such as increases in the abundance, distribution, and height of shrubs, result in Arctic “greening”, which has been detected since the late 1990s. Beginning in 2020, the Arctic has experienced a sequence of record- or near-record-high greenness values, to which 2025 is now added as the third highest value (section 5k). Local and regional variation is notable, however, with, for example, both greening and “browning” in the Eurasian Arctic. Vegetation changes in the Arctic are intrinsically connected to changes in permafrost as well. Since the 1980s, permafrost across the Arctic has seen a long-term warming trend, with the strongest trends in high-latitude, cold permafrost (section 5j). The active layer thickness, or the maximum depth of surface ground that seasonally thaws and freezes, has also increased, though at different regional rates.
Permafrost thaw is also a key player in Arctic terrestrial carbon dioxide and methane storage, though other important processes are also at play, such as wildfire, wetland development or loss, and river and lake outgassing. Examining tundra and boreal forest ecosystems in Arctic permafrost regions suggests that together carbon dioxide from these sources made the region a small net carbon dioxide source during the period 2000–20 (Sidebar 5.2). This is a serious and potentially long-term shift from Arctic permafrost regions acting as a carbon dioxide sink that dampens warming to a source that can enhance warming. Subannual records also show that the seasonal cycle of carbon storage and release is amplifying, reflecting both stronger winter emissions and stronger summer uptake (Sidebar 5.2).
Dramatic change continues for other frozen components of the Arctic system. On land, the Greenland Ice Sheet, which holds the second largest reservoir of frozen fresh water on the planet, had yet another year of overall ice loss (129±50 Gt based on gravity measurements; section 5g). Sixty percent of the planet’s glaciers and ice caps outside of Greenland and Antarctic are also found in the Arctic, and ice loss across these areas has tripled since the mid-1990s. During 2023/24, both Arctic Scandinavia and Svalbard had record years of ice loss with melt 1473% above the 1991–2020 mean in Arctic Scandinavia and 482% above in Svalbard (section 5h).
Arctic sea ice records also continue to show very low extent and predominantly first-year ice. The maximum sea ice extent in March 2025 was the lowest in the 47-year record, continuing a downward trend of −2.5% per decade, while September 2025 minimum extent was the 11th lowest on record, adding to a trend of −13.6% per decade extent loss (section 5f). Ice older than four years old is now nearly absent, with only 95,000 km2 of older ice in September 2025 as compared to 1.5 million km2 in the 1980s. Without sea ice cover, Arctic Ocean surface waters are exposed to heating from solar radiation and the atmosphere. Examined annually in August, the 2025 sea surface temperature in most Arctic Ocean regions was the highest in the 1982–2025 record and the pan-Arctic mean was the second highest on record (section 5e).
Pervasive environmental changes have direct and indirect impacts on people within and beyond the Arctic (e.g., Meng et al. 2023; Moon et al. 2019). In many instances, communities experience the combined impacts of multiple rapidly changing systems. For example, permafrost thaw and glacier retreat are increasing hazards such as glacial lake outburst floods, landslides, and the reliability of water supplies. Extreme weather hazards are also increasing. A prime example is the devastating ex-typhoon Halong that hit the Alaska west coast on 11–12 October 2025 (Sidebar 5.1). The storm traveled across anomalously warm ocean surface temperatures, and peak storm surge arrival on shore coincided with the daily high tide. Storm impacts were intense and widespread, including substantial inland and coastal flooding, ferocious winds, infrastructure loss, and loss of life.
The pace of change and the seriousness of impacts across plants, animals, and people highlight the importance of maintaining and strengthening our environmental intelligence regarding the Arctic region. Real threats to our scientific monitoring ability exist, such as the loss of a long-term Arctic vegetation monitoring dataset due to funding cuts (section 5k). This chapter’s observations show that the Arctic today is vastly different than the past, requiring close attention and increased action for hazard preparedness and response.