State of the Climate in 2023 - The Arctic

Arctic observations in 2023 provided clear evidence of rapid and pronounced climate and environmental change, shaped by past and ongoing human activities that release greenhouse gases into the atmosphere and push the broader Earth system into uncharted territory. This chapter provides a snapshot of 2023 and summarizes decades-long trends observed across the Arctic, including warming surface air and sea-surface temperatures, decreasing snow cover, diminishing sea ice, thawing permafrost, and continued mass loss from the Greenland Ice Sheet and Arctic glaciers. These changes are driving a transition to a wetter, greener, and less frozen Arctic, with serious implications for Arctic peoples and ecosystems, as well as for low- and midlatitudes. Average surface air temperatures for 2023 (January–December) for the Arctic as a whole were the fourth highest since 1900, with the Arctic summer (July–September) being the warmest on record. These unprecedented surface temperatures aligned with record-positive geopotential height anomalies in the polar troposphere, which have been increasing alongside warming air temperatures since 1958, indicating the strong connection between long-term atmospheric circulation and regional temperature patterns. Large-scale atmospheric circulation also strongly influences year-to-year variability and regional differences. For example, in 2023, a colder-than-normal spring across Alaska slowed snowpack and sea-ice melt, while parts of north-central Canada experienced their highest spring average temperatures on record. Short-term atmospheric events can also influence Arctic and midlatitude connections. A major Arctic sudden stratospheric warming (SSW) event in February 2023 is described in Sidebar 5.1—an event that can increase the likelihood of midlatitude cold-air outbreaks for several weeks to months, influencing subseasonal-to-seasonal predictability for midlatitude surface weather. Warming seasonal air temperatures together with the timing and extent of summer sea-ice loss significantly influence multi-decadal trends and the substantial regional and year-to-year variability seen across both marine and terrestrial systems. Driven by accelerated sea-ice retreat and melt that started in July, the September 2023 sea-ice monthly extent, which is the lowest monthly extent of the year, was 4.37 million square kilometers—about 10% lower than the past two years and overall the fifth lowest in the 45-year satellite record. Additionally, the 17 lowest September sea-ice monthly extents have all occurred in the last 17 years. Spring and early-summer sea-ice loss exposes the dark ocean surface and allows time for solar heating of the ocean. Linked to early sea-ice loss, average sea-surface temperatures for August 2023 were much higher than the 30-year average in the Barents, Kara, Laptev, and Beaufort Seas. Anomalously low August 2023 sea-surface temperatures were observed in Baffin Bay and parts of the Greenland, Bering, and Chukchi Seas. Despite considerable year-to-year variability, almost all Arctic Ocean and marginal seas studied show a statistically significant 1982–2023 warming trend. On land, the Arctic tundra is greening due to its sensitivity to rapidly increasing summer temperatures, as well as to rapidly evolving sea-ice, snow, and permafrost conditions. In 2023, circumpolar average peak tundra greenness was the third highest in the 24-year Moderate Resolution Imaging Spectroradiometer (MODIS) satellite record, a slight decline from the previous year. Closely aligned with air temperatures and nearshore sea-ice anomalies, peak vegetation greenness in 2023 was much higher than usual in the North American tundra, particularly in Brought to you by University of Colorado Libraries | Unauthenticated | Downloaded 09/23/25 10:40 PM UTC August 2024 | State of the Climate in 2023 5. The Arctic S284 the Beaufort Sea region. In contrast, tundra greenness was relatively low in the Eurasian Arctic, particularly in northeastern Siberia. Long-term changes in permafrost conditions are also largely controlled by changes in air temperature. Across all Arctic regions, permafrost temperatures and active layer thickness (i.e., thickness of the soil layer above the permafrost that seasonally thaws and freezes) continue to increase on decadal time scales. In 2023, permafrost temperatures were the highest on record at over half of the reporting sites across the Arctic. Permafrost thaw disrupts Arctic communities and infrastructure and can also affect the rate of greenhouse gas release to the atmosphere, potentially accelerating global warming. Analyses of Arctic precipitation reveal additional connections between a changing atmosphere and land. Precipitation in 2023 was above normal in all seasons for the Arctic as a whole, with short-duration heavy precipitation events breaking existing records at various locations. Arctic precipitation in the past year was also marked by important seasonal and regional variations. Unusually low precipitation and high temperatures produced severe drought and contributed to the record-breaking wildfire season in Canada’s Northwest Territory. Snowpack in early spring 2023 was above normal for North America and Eurasia, but then rapid snow loss in much of the Arctic resulted in record-low average snow-water equivalent for the North American Arctic in May and near-record-low snow cover for the Eurasian Arctic in June. Precipitation patterns also influence the Greenland Ice Sheet. Above-average snowfall over parts of the Greenland Ice Sheet between autumn 2022 and spring 2023 contributed to a relatively low (for the twenty-first century) total mass loss from the Greenland Ice Sheet despite extensive late-June-to-September ice melt. So, while the Greenland Ice Sheet lost mass in the past year, as it has every year since 1998, the loss for September 2022 to August 2023 was much lower than the 22-year average and similar to that of 2020/21. However, the cumulative melt-day area during summer 2023 was the second-highest in the 45-year satellite observational record. Beyond the Greenland Ice Sheet, the Arctic’s other glaciers and ice caps show a continuing trend of significant ice loss, especially in Alaska and Arctic Canada. All of the 25 monitored Arctic glaciers reported in this chapter for the 2022/23 mass balance year show an annual loss of ice, and for many glaciers these data indicate continued rapid wastage with substantial total contributions to global sea level. The exceptionally warm Arctic summer alongside persistent long-term climate changes contributed to a range of societal and environmental impacts in 2023 (see Sidebars 5.2 and 7.1), providing stark reminders of the varied climate disruptions that Arctic peoples and broader societies increasingly face. For example, Canada experienced its worst national wildfire season on record. Multiple communities in the Northwest Territories were evacuated during August, including more than 20,000 people from the capital city of Yellowknife. In August 2023 near Juneau, Alaska, a glacial lake on a tributary of the Mendenhall Glacier burst through its ice dam and caused unprecedented flooding and severe property damage on Mendenhall River, a direct result of dramatic glacial thinning over the past 20 years. With increasing seasonal shifts and widespread disturbances influencing the flora, fauna, ecosystems, and peoples of the Arctic, the need for ongoing observation and collaborative research and adaptation has never been higher.