Nina Kirchner, Jakob Kuttenkeuler, Riko Noormets, Elias Strandell Erstorp
The bathymetry of Lake Tarfala, located in a pro-glacial high alpine environment in the Kebnekaise mountains, northern Sweden, was mapped in September 2016. The mapping was made with an autonomous surface vessel, “ANKA”, designed to map shallow, uncharted waters. The survey had two objectives: (i) to acquire a modern bathymetric dataset of Lake Tarfala that can serve as a reference for future investigations of the lake dynamics. (ii) to test ANKA’s robustness, performance and endurance in a subpolar environment. The dataset includes a comparison with data from an earlier survey conducted in 1959.
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Citation
Nina Kirchner, Jakob Kuttenkeuler, Riko Noormets, Elias Strandell Erstorp (2019) Bathymetry of Lake Tarfala, northern Sweden. Dataset version 2. Bolin Centre Database. https://doi.org/10.17043/tarfala-kirchner-2017-bathymetry-2
References
Kirchner, N., Noormets, R., Kuttenkeuler, J., Strandell Erstorp, E., Schytt Holmlund, E., Rosqvist, G., Holmlund, P., Wennbom, M., Karlin, T. (2019): High-resolution bathymetric mapping reveals subaqueous glacial landforms in the Arctic alpine lake Tarfala, Sweden. Journal of Quaternary Science (in revision, April 2019)
Data description
This data has been acquired by Nina Kirchner, Jakob Kuttenkeuler, Elias Strandell Erstorp, and the autonomous surface vessel (ASV) "ANKA" in 2016. ANKA is equipped with an echosounder of type AIRMAR® EchoRange™ Smart™ Sensor, operated at 200kHz.
Data are provided in four xlsx files.
kirchner-2019-ANKA-all.xlsx contains 39581 raw soundings performed by ANKA, recorded with LON (column A) and LAT (column B) and depth (columns C and D). Mapping was carried out with an assumed sound velocity of 1500 m/s (column C) and corrected for the sound velocity in fresh water (1430 m/s) in column D.
kirchner-2019-ANKA-cleaned.xlsx contains 38598 soundings, resulting from a cleaning of the orginal ANKA dataset. Of the original 39581 ANKA soundings, 983 (approximately 2%) were disregard because they stem from positions already visited earlier by ANKA during the survey (to a seven place decimal accuracy in the decimal-degrees (lon/lat)). Therefore, the entire data set comprises soundings taken at the first visit of a spatial coordinate pairleaving a total of 38598 valid data-points, listed in column C.
For comparsion with the bathymetric chart available until 2016, data published 1960 by Larje and Nyberger was digitized. The file kirchner-2019-LN-all.xlsx contains 257 geo-referenced depth values corresponding to Larje and Nyberger's soundings. In kirchner-2019-LN-cropped.xlsx, 12 soundings have been removed because of no overlap with the ANKA data.
Comments
The ANKA dataset, containing more that 38000 depth-soundings, replaces the previously best-available bathymetric dataset of Lake Tarfala, derived from 257 depth-soundings conducted in 1959 and published in Larje and Nyberger (1960). A comparison of the two datasets shows that the map constructed from the 1960 data is surprisingly accurate despite it lacks exact GPS positioning, but that it was too coarse to reveal the glacial landforms at the bottom of the Lake which, however, become clearly visible in the high-resolution bathymetric data.
Literature reference:
Larje, R., Nyberger, L. (1960): Kartering av bottentopografien i Tarfalasjön (Mapping of bottom topography in Lake Tarfala). Naturgeografiska proseminariet, Stockholms Högskola.
The data files in Dataset Version 2 are commented in slightly more detail than in Version 1.
Video from mapping campaign
