Múlakvísl glacial flood in Iceland triggers toxic gas warnings

A glacial outburst flood, or jökulhlaup, is currently underway in the Múlakvísl river beneath the Mýrdalsjökull glacier in Iceland. The Icelandic Meteorological Office (IMO) reports that electrical conductivity in the river has risen sharply, reaching levels just over 500 µS/cm as of August 20, 2026. This unusually high conductivity indicates that geothermal meltwater is entering the river, a level comparable to a significant flood recorded in July 2017.

While the river level has not yet risen significantly, webcam observations show the water spreading across a wider area. There is an immediate concern regarding gas pollution; hydrogen sulphide (H2S) concentrations at the Láguhvolar monitor, located approximately 2 km from the margin of Kötlujökull, have exceeded health-protection limits.

Authorities have advised the public to avoid lingering near Múlakvísl or the glacier margin, noting that calm weather may cause toxic gas to accumulate in low-lying depressions. Individuals experiencing nose or eye irritation are instructed to leave the area immediately.