Nina Kirchner, Annika Granebeck, Daniella Lillieroth Charalambous
This dataset contains images of Lake Tarfala taken every 2 hours during the period from 1 June to 18 July 2021. During this period, the surface of Lake Tarfala 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 (or, rather, a time interval) 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 Lake Tarfala’s north-eastern shore, at 1220 m above sea level. In total, there are 432 images.
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Scientific highlights
This dataset allows to assign a precise date to the ice-off event at Lake Tarfala in summer 2021. 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 12 July 2021.
Precise knowledge of the ice-off date can be used to:
- Assist in understanding lake mixing processes.
- Better constrain numerical models computing ice-off.
- Provide a complement to ice-off dates derived from satellite imagery, which is notoriously difficult in polar alpine environments due to persistent cloud cover and long polar nights.
- Lend support to alternative definitions of ice-off.
- Contribute to knowledge of lake ice phenology in high altitude Arctic environments under current climate change.
Some notable events in the time-lapse imagery of the diminishing lake ice cover include:
- 2 – 7 June: Retreat of ice cover along eastern lake shoreline (foreground of the picture, most visible 7 June at 23:05) in conjunction with onset of streamwater influx from stream system on the eastern lake bank (2 June from 01:05).
- 9 – 12 June: Increasing number of melt features on the central lake ice cover, mimicking surface meltwater ponds (most visible 9 June at 17:05 and 19:05).
- 21 – 23 June: Pronounced melting of ice cover in the north-western lake-corner where Kebnepakte Glacier drains into Lake Tarfala (right margin of picture, most visible 21 June at 19:05 and 23 June at 21:05).
- 6 – 9 July: Lakewide drift of ice floes, initially concentrated in the central, southern and eastern parts of the lake (6 July at 00:00 until 7 July at 8:00), subsequently concentrating in the northern lake-corner (7 July, from 12:00 until 14:00) and lastly, in the southern lake-corner where the lake outflow is located (8 July at 00:00 until 9 July at 22:00).
- 10 – 12 July: Final drift and disintegration of the season’s last ice floes.
- 17 July: Inflow of sediment-rich streamwater from stream network on the eastern lake bank (left margin of picture, at 04:00 until 12:00).
Due to complications with the date-and-time-stamp function of the camera, incorrect dates and times are shown in the images taken between 1 – 23 June. In the slide show here, correct time points in this interval can be deduced by adding 1 hour and 5 minutes to those indicated in the slider.
Because of battery failure, no pictures were taken between 24 June and 5 July. To indicate this in the slide show, pictures in the time interval are rendered blurry.
During 6 – 18 July, times are correctly shown both in the photos and in the slider.
Note that the camera produces black-white images under certain light conditions, such as under some low-visibility weather conditions.
Citation
Nina Kirchner, Annika Granebeck, Daniella Lillieroth Charalambous (2023) Time lapse imagery of the ice-off event at Lake Tarfala, Kebnekaise Mountains, northern Sweden, summer 2021. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/tarfala-kirchner-2023-ice-off-2021-1
Data description
The dataset consists of image files (JPG
) of Lake Tarfala, with the date and time (Swedish daylight saving time, UTC+2) included in each photo. Due to complications with the date-and-time-stamp function of the camera during parts of the measurement series, incorrect dates and times are shown in the images taken between 1 and 23 June. Please refer to image file names for corrected dates and times, which follow the YYYYMMDD_HHMM
format. Because of battery failure, no pictures were taken between 24 June and 5 July.
The pictures were acquired using a camera positioned on the mountain flank along Lake Tarfala’s north-eastern shore, at ~67.9° N, 18.6° E, at 1220 m above sea level.
The data were collected using a SiFar Willfine Trail Camera 4.0CG. 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 ~394 MB.
During a few short periods, fog, snow and/or rain obscures the view of the lake.
Comments
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.