Another glacial outburst flood begins at the Vatnajökull ice cap, Iceland

Another glacial outburst flood (jökulhlaup) is in progress at the Vatnajökull ice cap since September 5, 2021. Yesterday’s flood started at the Eastern Skaftárketill cauldron and follows another flood from the Western Skaftárketill which began on September 1. This will significantly add to current flood levels in the Skaftá river, the Icelandic Met Office (IMO) said.

Björn Oddsson, a geophysicist for the Department of Civil Protection and Emergency Management, told the mbl.is that the floodwater can be expected to reach the Ring Road tonight, September 6.¹

“The people who live here and travel in this area know precisely where the Skaftá glacial outburst floods have an effect. Roads in the area could close, and a great deal of silt and mud could spread around the area and be carried with the wind once the area dries.”

Measurements show the surface of the cauldron has subsided 1 m (3.3 feet) between 23:00 UTC on September 4 and 12:45 UTC on September 5.

Maximum discharge during floods from the Eastern cauldron has previously reached 3 000 m³/s (106 000 feet³ per second) but the last flood in 2018 peaked at 2 000 m³/s (70 600 feet³ per second). If compared to the flood in 2018 the first hydrological station will see the first signs of floodwater in the morning of September 6. 

The event follows another glacier outburst flood from the Western Skaftárketill which began on September 1.²

A flood from the eastern cauldron has not occurred since 2018, and this one is expected to be about as large as that year’s flood. The flood in 2015 was considerably larger and caused more damage.

Glacial outbursts in the Skaftá river originate in a geothermal area under depressions in the ice cap of the Vatnajökull glacier called Skaftárkatlar. These depressions are formed when geothermal heat melts enough ice to create an outburst flood.

When the outburst takes place, the meltwater first flows a distance of 40 km (25 miles) under the ice cap and then a distance of 28 km (17 miles) along the river bed of Skaftá river, before reaching Sveinstindur mountain. It then takes about 10 hours for floodwaters to reach the Ring Road near Ásar by Eldvatn lake.