Nina Kirchner, Annika Granebeck, Johanna Dahlkvist, Jamie Barnett, Daniella Lillieroth Charalambous
This dataset contains images of Darfáljávri taken every 2 hours (irrespective of day- or nighttime) during the period from 17 September, 2023 to 20 October, 2023. During this period, the surface of Darfáljávri transitions from being ice-free to ice-covered, an event referred to as "ice-on".
The dataset can be used to observe the ice-on 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-on 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 400 images. The later the season, the more pictures are dark because of the approaching of the polar night.
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Scientific highlights
This dataset allows to assign a precise date to the ice-on event at Darfáljávri in autumn 2023. Defining ice-on as the first occasion after the ice-free summer season on which the lake becomes completely ice-covered and remains so for the rest of the winter, it was attained on 12 October, 2023.
Some notable events in the time-lapse imagery of the establishing lake ice cover include:
Pre-ice-on
- 17 September: Pronounced ripples on lake surface (picture 4).
- 23 September: Inflow of sediment-rich streamwater from stream network on the eastern lake bank (picture 73).
- 10 October: First occasion of thin ice layer formation on central lake surface (picture 277), subsequently becoming snow covered (picture 282) and gradually expanding towards lake margins (picture 289).
Ice-on
- 12 October: First occasion of clearly identifiable ice cover across the entire lake surface (picture 301). Crack formation in southeastern lake corner (picture 313).
- 15 October: Patterning of snow cover on frozen lake surface (picture 339).
- 18 October: Thickening of ice cover and establishment of continuous overlying snow cover (picture 374).
Picture numbers in the scientific highlights correspond to picture numbers in the dataset. Note that the camera produces black-white images under certain light conditions, such as during dusk and dawn and under some low-visibility weather conditions.
Citation
Nina Kirchner, Annika Granebeck, Johanna Dahlkvist, Jamie Barnett, Daniella Lillieroth Charalambous (2025) Time lapse imagery of the ice-on event at Darfáljávri (Lake Tarfala), Kebnekaise mountains, northern Sweden, autumn 2023. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/tarfala-kirchner-2025-ice-on-2023-1
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 ~2.6 MB. The total size of the dataset is ~970 MB.
During a few short periods, fog, snow and/or rain obscures the view of the lake. Also, due to shorter periods of daylight during autumn, the number of dark images between dusk and dawn successively increases.