TY - JOUR
T1 - Development of a subglacial lake monitored with radio-echo sounding
T2 - Case study from the eastern Skaftá cauldron in the Vatnajökull ice cap, Iceland
AU - Magnússon, Eyjólfur
AU - Pálsson, Finnur
AU - Gudmundsson, Magnús T.
AU - Högnadóttir, Thórdís
AU - Rossi, Cristian
AU - Thorsteinsson, Thorsteinn
AU - Ófeigsson, Benedikt G.
AU - Sturkell, Erik
AU - Jóhannesson, Tómas
N1 - Publisher Copyright:
© 2021 The Author(s).
PY - 2021/8/12
Y1 - 2021/8/12
N2 - We present repeated radio-echo sounding (RES, 5gMHz) on a profile grid over the eastern Skaftá cauldron (ESC) in Vatnajökull ice cap, Iceland. The ESC is a g1/4g3gkm wide and 50-150gm deep ice cauldron created and maintained by subglacial geothermal activity of g1/4g1gGW. Beneath the cauldron and 200-400gm thick ice, water accumulates in a subglacial lake and is released semi-regularly in jökulhlaups. 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 (0.5-4.1gkm2) 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 250gGL (gigalitresgCombining double low lineg106gm3) in June 2015, but 320g±g20gGL drained from the ESC in October 2015. In June 2018, RES profiles revealed a lake volume of 185gGL, while 220g±g30gGL were released in a jökulhlaup in August 2018. Considering the water accumulation over the periods between RES surveys and jökulhlaups, this indicates 10g%-20g% uncertainty in the RES-derived volumes at times when significant jökulhlaups may be expected.
AB - We present repeated radio-echo sounding (RES, 5gMHz) on a profile grid over the eastern Skaftá cauldron (ESC) in Vatnajökull ice cap, Iceland. The ESC is a g1/4g3gkm wide and 50-150gm deep ice cauldron created and maintained by subglacial geothermal activity of g1/4g1gGW. Beneath the cauldron and 200-400gm thick ice, water accumulates in a subglacial lake and is released semi-regularly in jökulhlaups. 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 (0.5-4.1gkm2) 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 250gGL (gigalitresgCombining double low lineg106gm3) in June 2015, but 320g±g20gGL drained from the ESC in October 2015. In June 2018, RES profiles revealed a lake volume of 185gGL, while 220g±g30gGL were released in a jökulhlaup in August 2018. Considering the water accumulation over the periods between RES surveys and jökulhlaups, this indicates 10g%-20g% uncertainty in the RES-derived volumes at times when significant jökulhlaups may be expected.
UR - http://www.scopus.com/inward/record.url?scp=85112796148&partnerID=8YFLogxK
U2 - 10.5194/tc-15-3731-2021
DO - 10.5194/tc-15-3731-2021
M3 - Article
AN - SCOPUS:85112796148
SN - 1994-0416
VL - 15
SP - 3731
EP - 3749
JO - Cryosphere
JF - Cryosphere
IS - 8
ER -