Snow and ground frost depths were measured at a boreal fen close to Oulanka research station, northeastern Finland (66°22'N, 29°19'E) in years 1980 to 2023, as part of ongoing long-term surveys conducted by the research station staff. Data were collected manually by reading snow depths on survey sticks placed at the fen on fixed locations once per week. Ground frost depths were manually recorded by visually inspecting hollow tubes placed inside the snow depth survey sticks containing water and ink. The level of frozen coloured water was thus observed. The site is outside permafrost zone, so only the top layer of the soil freezes during winter. The data consists of separate weekly values of six (1980-2002) or seven (2007-) survey sticks, and of average values for the snow depth and ground frost depth. The data has two missing seasons; 1981-1982 and 2002-2003, and for 1989-1991 only ground frost depth was recorded. 2004 to 2007 the data consists of only one measurement stick. […]
