Development of a subglacial lake monitored with radio-echo sounding: case study from the eastern Skaftá cauldron in the Vatnajökull ice cap, Iceland
<p>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 a <span class="inline-formula">∼</span> 3 km wide and 50–150 m deep ice cauldron created and maintained by subglaci...
| Main Authors: | , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-08-01
|
| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/15/3731/2021/tc-15-3731-2021.pdf |
| Summary: | <p>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 a <span class="inline-formula">∼</span> 3 km wide and 50–150 m deep ice
cauldron created and maintained by subglacial geothermal activity of
<span class="inline-formula">∼</span> 1 GW. Beneath the cauldron and 200–400 m thick ice, water
accumulates in a subglacial lake and is released semi-regularly in
<i>jökulhlaups</i>. The RES record consists of annual surveys conducted at the
beginning of every summer during the period 2014–2020. Comparison of the RES
surveys reveals variable lake area (0.5–4.1 km<span class="inline-formula"><sup>2</sup></span>) 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 pre- and
post-jökulhlaup surface DEMs. The estimated lake volume was 250 GL
(gigalitres <span class="inline-formula">=</span> 10<span class="inline-formula"><sup>6</sup></span> m<span class="inline-formula"><sup>3</sup></span>) in June 2015, but 320 <span class="inline-formula">±</span> 20 GL drained from the ESC in
October 2015. In June 2018, RES profiles revealed a lake volume of 185 GL,
while 220 <span class="inline-formula">±</span> 30 GL were 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.</p> |
|---|---|
| ISSN: | 1994-0416 1994-0424 |