Climate and bioclimatic conditions of Kolguev Island (Barents Sea)

This study assesses climatic and bioclimatic variability on Kolguev Island (Barents Sea) using meteorological observations from the Kolguev Severny station for 1941-2024 and expedition measurements conducted in June-July 2023 and 2025. Trends in air temperature, precipitation, frost-free and growing seasons were analyzed, while bioclimatic conditions were evaluated using the Universal Thermal Climate Index (UTCI). A statistically significant increase in air temperature was identified in all seasons, with a pronounced intensification after 2000. Mean annual temperature increased by 0.27 °C per decade during 1941-2024 and by 0.89 °C per decade during 2000-2024. The spring transition of air temperature across 0 °C shifted to earlier dates, while the autumn transition shifted later, resulting in an increase in the frost-free period from 146 days (1961-1990) to 157 days in the 1991-2020. The duration of the growing season increased by about one month, and the sum of positive temperatures rose by 117 °C. During the second decade of the 21st century, a tendency toward decreasing moisture availability on the island has also been observed. Bioclimatic conditions on Kolguev Island are dominated by cold stress of varying intensity according to the UTCI classification, ranging from extreme to slight cold stress. The frequency of extreme cold stress decreased from 18% of days in the 1970s to 9% in the 2010s, while the proportion of days without thermal stress in summer increased from 4% to 7%. Expedition observations showed prevailing strong and moderate cold stress conditions, although rapid changes from very strong to moderate cold stress may occur within hours due to weakening winds. The observed climatic changes contribute to Arctic "greening," increasing vegetation productivity and potentially affecting tundra ecosystems, reindeer herding, and biodiversity.