Development of a subglacial lake monitored with radio-echo sounding: case study from the eastern Skaftá cauldron in the Vatnajökull ice cap, Iceland
| Autor: | Thórdís Högnadóttir, Benedikt G. Ófeigsson, Cristian Rossi, Finnur Pálsson, Eyjólfur Magnússon, Thorsteinn Thorsteinsson, Erik Sturkell, Tómas Jóhannesson, Magnús T. Gudmundsson |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Radio-Echo Sounding
geography QE1-996.5 geography.geographical_feature_category Bedrock DEM Iceland Borehole Jökulhlaup Geology Environmental sciences Depth sounding Echo sounding Subglacial lake GE1-350 TanDEM-X Subglacial lakes Digital elevation model Geomorphology Geothermal gradient Earth-Surface Processes Water Science and Technology |
| Zdroj: | The Cryosphere, Vol 15, Pp 3731-3749 (2021) |
| ISSN: | 1994-0424 1994-0416 |
| Popis: | We present repeated radio-echo sounding (RES, 5 MHz) on a profile grid over the Eastern Skaftá Cauldron (ESC) in Vatnajökull ice cap, Iceland. The ESC is ~3 km wide and 50–150 m deep ice cauldron created and maintained by subglacial geothermal activity of ~1 GW. Beneath the cauldron and 200–400 m thick ice, water accumulates in a lake and is released semi-regularly in jökulhlaups. The RES record consists of annual surveys with 200–400 m between profiles in early summers of 2014–2020. Comparison of the RES surveys (2D migrated profiles) reveals variable lake area (0.5–4.1 km2) and enables traced reflections from the lake roof to be distinguished from bedrock reflections. This allows construction of a digital elevation model (DEM) of the bedrock in the area, further constrained by two borehole measurements at the cauldron centre. It also allows creation of lake thickness maps and an estimate of lake volume at the time of each survey, which we compare with lowering patterns and released water volumes obtained from surface DEMs obtained before and after jökulhlaups. The estimated lake volume is 250 × 106 m3 in June 2015 but 320 ± 20 × 106 m3 drained from the cauldron in October 2015. In June 2018, RES profiles reveal a lake volume of 185 × 106 m3 while 220 ± 30 × 106 m3 was released in a jökulhlaup in August 2018. Considering the water accumulation over the periods between RES surveys and jökulhlaups, this indicates 10–20 % uncertainty in the RES-derived volumes at times when significant jökulhlaups may be expected. |
| Databáze: | OpenAIRE |
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