Glacial outburst flood at Grimsvotn caldera, Iceland

Sentinel-2 MSI acquired on 10 October 2021 at 12:43:09 UTC
Sentinel-1 CSAR IW acquired on 17 November 2021 at 18:50:48 UTC
Sentinel-1 CSAR IW acquired on 11 December 2021 at 18:50:47 UTC
Author(s): Sentinel Vision team, VisioTerra, France -
Keyword(s): Geohazard, polar, cryosphere, ice cap, glacier, volcano, river, flood, hydrology, Iceland
Fig. 1 - COP DEM - The Grímsvötn is a subglacial volcano located under the northwestern side of the Vatnajökull ice cap in Iceland.
Fig. 2 - S2 (10.10.2021) - A jökulhlaup (glacial outburst flood) was reported, due to subsidence of the ice shelf in Grímsvötn’s caldera.
Fig. 3 - S1 (mean 17, 19 & 23.11.2021) - Subsidence of the ice shelf into the underlying lake had begun around 24 Nov. in an area SE of Grímsfjall.
Fig. 4 - S1 (mean 05, 07 & 11.12.2021) - Rising waters were first detected in that river overnight during 30 November-1 December.
Water from the lake drained from the E side of Skeiðarárjökull and from a channel in the middle of a trail into the Gígjukvísl River.
Fig. 5 - S1 (red & blue channels: 17, 19 & 23.11.2021; green channel: 05, 07 & 11.12.2021) - By 6 Dec. the ice shelf had subsided a total of ~77m.
By 2 December the flow rate in the river was 930 cubic meters per second, triple what was detected three days before, and 10 times the normal seasonal rate. Daily measurements showed that the flow rate continued to rise, likely peaking at 2800 cubic meters per second during the morning of 5 December. The data indicated that the lake was mostly empty of water by 6 December.