Water temperatures from the arctic-alpine Lake Tarfala (Darfáljávri), Northern Sweden, 2019 – 2020 and 2021 – 2022

Nina Kirchner, Joachim Jansen

This dataset provides measurements of water temperature recorded in the glacier-proximal arctic-alpine Lake Tarfala in the Kebnekaise Mountains, Northern Sweden.

These data were collected in order to investigate Lake Tarfala's thermal state and its cryostratification patterns, and in relation to its ice-phenology (ice-off and ice-on) as observed from time lapse imagery.

Water temperatures were acquired between September 2019 and September 2020, and between September 2021 and August 2022. Measurements were taken in the central and deepest part of the lake, at water depths ranging between 2 m and 40 m, every 15 – 30 minutes. During 2021 – 2022, subsurface water pressure was also measured. Importantly, this dataset contains year-round measurements, starting in the ice-free season, continuing through the ice-covered season, and transitioning into the ice-free season again. Under-ice measurements can be challenging, as illustrated by the 2020 – 2021 loss of instruments and all data stored on them, causing a yearlong gap in the dataset which itself is a continuation from records spanning the years 2016 – 2019.

Citation

Nina Kirchner, Joachim Jansen (2023) Water temperatures from the arctic-alpine Lake Tarfala (Darfáljávri), Northern Sweden, 2019 – 2020 and 2021 – 2022. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/tarfala-kirchner-2023-lake-temperature-1

References

Kirchner, N., Weckström, J., Jansen, J., Schenk, F., Barnett, J., Granebeck, A., Leppäranta, M., Korhola, A. 2023. Water temperature, mixing and ice phenology in the arctic-alpine lake Darfáljávri (Lake Tarfala), northern Sweden. Arctic, Antarctic and Alpine Research (in revision)

Kirchner, N., Kuttenkeuler, K., Rosqvist, G., Hancke, M., Granebeck, A., Weckström, J., Weckström, K., Schenk, F., Korhola, A., Eriksson, P., 2021. A first continuous three-year temperature record from the dimictic arctic-alpine Lake Tarfala, northern Sweden. Arctic, Antarctic, and Alpine Research, 53:1, 69-79, https://doi.org/10.1080/15230430.2021.1886577

Data description

Data were acquired in the central part of Lake Tarfala, located at 67° 55’ 28’’ N, 18° 35’ 22’’ E and an elevation of 1162 m above sea level, using instruments anchored to a mooring line. The instruments logged, time-stamped (UTC+2) and saved the water temperature every 30 minutes during 2019-2020 and every 15 minutes during 2021-2022. An exception is the pressure sensor (also recording water temperature) which acquired measurements every 30 minutes starting in 2021.

Data are provided in csv-files

1. WaterTemp2019-2020.csv contains 17929 date- and timestamped water temperature measurements at 38 m, 28 m, 18 m, 8 m, 4 m and 2 m water depths. Data is from HOBO Water Temp Pro v2 profilers and Seabird Scientific SBE56 temperature sensors (for details, see Reference provided) with the following columns:

   1. Date (YYYY-MM-DD): Date in the format year-month-day
   2. Time (HH:MM:SS): Time in the format hours-minutes-seconds
   3. 38 m: water temperatures at 38 m water depth
   4. 28 m: water temperatures at 28 m water depth
   5. 18 m: water temperatures at 18 m water depth
   6. 8 m: water temperatures at 8 m water depth
   7. 4 m: water temperatures at 4 m water depth
   8. 2 m: water temperatures at 2 m water depth

2. WaterTemp2021-2022.csv contains 32159 date- and timestamped water temperature measurements (degrees Celsius) at 40 m, 30 m, 20 m, 10 m, 4 m, 3 m and 2 m water depths. The pressure sensor (at 3 m water depth) renders also water temperature, but only every 30 minutes (see above). Time instances for which no data is available from 3 m water depth is indicated by NaN. Data is from HOBO U22 Water Temp Pro v2 profilers and Seabird Scientific SBE56 temperature sensors (for details, see Reference provided) with the following columns:

   1. Date (YYYY-MM-DD): Date in the format year-month-day
   2. Time (HH:MM:SS): Time in the format hours-minutes-seconds
   3. 40 m: water temperatures at 40 m water depth
   4. 30 m: water temperatures at 30 m water depth
   5. 20 m: water temperatures at 20 m water depth
   6. 10m: water temperatures at 10 m water depth
   7. 4 m: water temperatures at 4 m water depth
   8. 3 m: water temperatures at 3 m water depth
   9. 2 m: water temperatures at 2 m water depth

3. WaterPressure2021-2022.csv contains 16080 date- and timestamped water pressure measurements (in kPa = kilopascal) at 3 m water depth. Data is from a HOBO U22 Water Level Logger (for details, see Reference provided) with the following columns:

   1. Date (YYYY-MM-DD): Date in the format year-month-day
   2. Time (HH:MM:SS): Time in the format hours-minutes-seconds
   3. Pressure (kPa): water pressures at 3 m water depth

Photography

dji_fly_20230724_121706_821_1690194707773_photo.jpg photo of Lake Tarfala by Florian Vacek.

Note

When the mooring was retrieved on September 14, 2020, it had collapsed and was retrieved with all sensors and the mooring line bundled together, and with lake sediments on the mooring line. We believe that the mooring collapsed in July 2020, during the ice-off process. Indirect evidence are the very similar water temperatures at all depths after July 25, 2020, which we chose to not remove from the dataset since we do not have any direct proof for a collapse of the mooring.

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, F. Schenk, A. Granebeck) is gratefully acknowledged. Tarfala Research Station staff, especially Torgny Lundberg and Martin Houssais, are thanked for support in the field. The dataset is a continuation of earlier measurements, see tarfala-kirchner-2020-lake-temperature-1.