A jøkulhlaup or Glacier Lake Outburst Flood (GLOF) is a sudden release of water from a glacier.
The sudden release of water from a glacier is called a jøkulhlaup or Glacier Lake Outburst Flood (GLOF). The water source can be a glacier-dammed lake, a pro-glacial moraine-dammed lake or water stored within, under or on the glacier. Once the water finds a way over, underneath or through the dam, large parts of the lake can be emptied in a short time (hours to days) resulting in violent floods. Such floods have caused considerable damage in the past. The term jøkulhlaup is Icelandic in origin (from the Icelandic jøkull = glacier, and hlaup = flood burst).
One way to reduce the risk of such a flood is the controlled drainage of the trapped water through artificial spillways or tunnels, either to empty the lake or to lower its level below a critical level. This has been done several glacier-dammed lakes, including at Demmevatnet (Hardangerjøkulen) and at Austerdalsisen (Svartisen).
In cases where there is no mitigation work carried out and there is thought to be potential for a glacier flood, then the glacier lake should be monitored closely.
Jøkulhlaups in Norway in recent years
- Øvre Messingmalmvatnet at Rundvassbreen, Blåmannsisen in Nordland - first event in 2001, then in 2005, 2007, 2009, 2010, 2014, 2016, 2018 and 2019. Volume of flood in each event between 10 and 36 million m3.
- Nupsfonn in the county of Vestland, northwest of Ståvatnet. One registered event in August 2019 with a volume pf about 10 million m3.
- Demmevatnet at Rembesdalskåka (an outlet glacier of Hardangerjøkulen) in Eidfjord, Hordaland. The first registered event was in 1736 and there were several damaging occurrences until 1937, when the second tunnel constructed to lower lake level was completed. The glacier has become thinner in recent years and there have been six events since 2014, the most recent in August 2019.
- Harbardsbreen in Luster, Sogn og Fjordane had jøkulhlaups almost every year between 1996 and 2001, and had two big floods in 2010 and 2015 (up to 10 million m3 of water).
- Koppangsbreen in Lyngen - first registered event in 2010, then in 2011, 2012 (two events), 2013 (nine events in one summer) and the most recent event in 2014.
- Tystigbreen in Stryn - events in 2010, 2014 and 2018.
- Flatbrevatnet at Flatbreen, Jostedalsbreen in Sogndal, Sogn og Fjordane in 1924, 1947 and 2004. In the most recent event at least 50 000 m3 of water caused a debris flow of over 200 000 m3.
- Heiavatnet at Svartisheibreen, Vestre Svartisen in Rana, Nordland - six known events between 1989 and 2016.
An overview of all known jøkulhlaups in Norway up to and including 2014 is given in the report: Inventory of glacier-related hazardous events published by NVE in 2014. The report describes each jøkulhlaup event, as well as other glacier incidents such as icefalls from glaciers, events related to rapid glacier advance or retreat, and accidents associated with glacier hiking and climbing.
An updated overview of all recorded events in Norway is shown on the map here.
An overivew of events up to 1954 was published by Olav Liestøl in "Glacier dammed lakes in Norway". Norsk geografisk tidsskrift, Volume 15, pp. 122-149. The article gives detailed descriptions of events at:
- Sauavatnet at Søndre Folgefonn in Etne, Hordaland
- Brimkjellen atTunsbergdalsbreen, Jostedalsbreen in Luster, Sogn og Fjordane
- Demmevatnet at Hardangerjøkulen in Eidfjord, Hordaland
- Austerdalsvatnet at Østre Svartisen in Rana, Nordland
- Øvre Mjølkedalsvatn at Mjølkedalsbreen, Jotunheimen in Lom, Oppland
- Skadevatnet at Vetlefjordbreen, Jostefonn in Balestrand, Sogn og Fjordane
- Koldevatnet, Tafjord in Valldal, Møre og Romsdal
Gridabase is a database with information on glacier-related events and accidents that was established in the EU project Glaciorisk (2001-03). NVE and the Department of Geosciences in the University of Oslo participated in the project, as well as groups in Iceland, France, Switzerland and Italy.