Time lapse imagery of the ice-off event at Darfáljávri (Lake Tarfala), Kebnekaise mountains, northern Sweden, summer 2025
Nina Kirchner, Johanna Dahlkvist, Tarfala Research Station staff
This dataset contains images of Darfáljávri taken every 2 hours (irrespective of day- or nighttime) during the period from 07 July, 2025 to 31 July, 2025. During this period, the surface of Darfáljávri transitions from being ice-covered to ice-free, an event referred to as "ice-off".
The dataset can be used to observe the ice-off event and to assign a date to it. Knowledge of lake ice phenology, i.e. seasonal formation and loss of the lacustrine ice cover, is of importance since the timing of ice-off impacts lake processes such as stratification and vertical mixing.
The pictures were acquired using a camera positioned on the mountain flank along Darfáljávri’s north-eastern shore, at 1220 m above sea level. In total, there are 313 images.
LacustrineObservationsDarfáljávriLake TarfalaTarfalaLake iceLake ice phenologyIce-off
Download dataScientific highlights
This dataset allows to assign a precise date to the ice-off event at Darfáljávri in summer 2025. Defining ice-off as the first occasion after the ice-covered winter season on which the lake becomes completely ice-free and remains so for the rest of the summer, it was attained on 31 July, 2025.
Some notable events in the time-lapse imagery of the diminishing lake ice cover include:
- 6 July: Commence of ice cover melt in the northwestern lake corner where Kebnepakte Glacier drains into Darfáljávri (picture 1).
- 8 July: Pronounced melting of ice cover in the north-western lake-corner where Kebnepakte Glacier drains into Lake Tarfala (picture 27).
- 15 – 20 July: Weakening of central ice cover through cracking and melting (e.g. picture 102– 165 ) followed by rapid onset of lakewide drift and disintegration of ice floes (picture 185).
- 22 July: Ice break away from shore and drift along the eastern lake shoreline where stream water from southeastern Kaskasatjåkka glacier drains into Darfáljávri (starting in foreground of picture 187).
- 23 – 30 July: Final drift and disintegration of the season’s last ice floes.
- 31 July: “Ice off”.
Picture numbers in the scientific highlights correspond to picture numbers in the dataset.
Name
Version
Citation
References
Kirchner N, Weckström J, Jansen J, Schenk F, Barnett J, Granebeck A, Leppäranta M, Korhola A (2024) Water temperature, mixing, and ice phenology in the arctic–alpine Lake Darfáljávri (Lake Tarfala), northern Sweden. Arctic, Antarctic, and Alpine Research 56. https://doi.org/10.1080/15230430.2023.2287704
Data description
The dataset consists of image files (JPG) of Darfáljávri, with the date and time (Swedish daylight saving time, UTC+2) included in each photo. Image file names are numbered in chronological order.
The pictures were acquired using a camera positioned on the mountain flank along Darfáljávri’s north-eastern shore, at ~67.9° N, 18.6° E, at 1220 m above sea level.
The data were collected using a Hunter Orion Trail Camera 4G. The camera elevation is 1.8 m above ground. Each JPG file has a size of ~1 MB. The total size of the dataset is ~0.31 GB.
During a few short periods, fog, snow and/or rain partly obscure the view of the lake.
Project
The data were collected as part of a project within the Arctic Avenue Spearhead Research project between Stockholm University and the University of Helsinki, Finland, running between 2019 and 2022. Data is collected solely by Tarfala Research Station since 2023. The support of our co-workers on the Arctic Avenue activity Lake thermal and mixing dynamics under changing climate (J. Weckström, K. Weckström, A. Korhola, and F. Schenk) is gratefully acknowledged.
Publisher
Bolin Centre Database
License
Creative Commons Attribution 4.0 International License (CC BY 4.0)
First name
Johanna
Last name or organisation
Dahlkvist
Email address
Address
Tarfala Research Station, c/o Baltic Sea Centre; Stockholm University
Postal code
SE-106 91
City
Stockholm
Country
Sweden
GCMD science keyword
Earth science > Cryosphere > Snow/ice > Lake ice
GCMD location
Continent > Europe > Northern Europe > Scandinavia > Sweden
Dataset language
English
Begin date
2025-07-07
End date
2025-07-31