The dataset presents semi-manually delineated polygons of retrogressive thaw slumps (RTSs) at five key sites (G1, G2, G3, Y1, Y2) in the West Siberian Arctic, particularly in Gydan and Yamal peninsulas. The delineation was performed based on CORONA (1964, 1969), HEXAGON (1972, 1977, 1982, 1984), and PlanetScope (2024) satellite images. Each polygon delineated based on historical images (CORONA or HEXAGON) was assigned with unique ID (RTS name [] field), some of which correspond to the RTS IDs from the dataset by Nesterova et al. (2025). RTS polygons were also classified with a corresponding numerical code. An additional field of the confidence level included three categories: 1 – confident, 2 – uncertain, and 3 – no data / no confidence. RTS polygons delineated based on PlanetScope 2024 images consist of a state field describing manual or automatic mapping. More details on the delineation and classification methods are described in Nesterova et al. (2025).

• The files of RTS polygons are in GEOJSON vector format. The naming follows the logic: Key site name + year. The polygons of 1964, 1969, 1972, 1977, 1982, 1984 consist of the following fields: RTS_name of unique RTS ID, notes of a numerical code of classification, Confidence_Level of the confidence three categories. The polygons of 2024 consist of the following fields: RTS name [] of unique RTS ID, state indicating manual or automatic mapping method.* All detailed information on delineation and classification methods can be found in Supplementary Information 2 of Nesterova et al. (2025). Funded by "Der Deutsche Akademische Austauschdienst (DAAD) - STIBET I", google.org " Impact Challenge on Climate Innovation to the Permafrost Discovery Gateway development", BMWK "ML4EARTH" and the "Planet Research Program"