From November 24 to December 2, 2021, the Grimsvöttn Glacier subsided by about 17 meters. That’s about 9 days since it began to subside, and flowing water began to work its way under the glacier.
Hydrologists at the Meteorological Office measured the flow at Gigyukvistle around 11:00 UTC on December 2, which was then nearly 930 m3/s, and the flow had nearly tripled in three days, the Icelandic Meteorological Office said in an update published at 16:00 UTC on December 2, 20211.
This flow is 10 times the flow in the river compared to last season.
Electrical conductivity, which indicates the amount of flowing water in the river, has also increased in recent days and was measured at 272 μS/cm at 13:00 UTC December 2 and continues to increase. Gas has been detected in small amounts in the tail of the glacier and is within the danger level.
“The latest measurements agree fairly well with the flow predictions that have been made and suggest that the flooding will probably peak next Sunday. If there is a significant change in the development of the flow from Grimsvötn, it will affect when the flooding will peak,” IMO said.
There are examples of eruptions in Grimsvötn after water flows out of there.
“The last time it happened was in 2004, and before that in 1934 and 1922.