Glacier dammed lake at Harbardsbreen in Sogn og Fjordane county, after emtying 20.-24. August 2015. Photo: Hallgeir Elvehøy

A jøkulhlaup or Glacier Lake Outburst Flood (GLOF) is a sudden release of water from a glacier. 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 within 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).

An established mechanism to reduce the risk of a violent outburst 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 e.g. at Demmevatnet (Hardangerjøkulen) or at Austerdalsisen (Svartisen).

When such controlling interventions are not practicable or the urgency of the situation does not leave sufficient time to drain the lake water, a reliable and operational forecast and warning system is desirable. However, the incomplete understanding of outburst flood initiation complicates any prediction.

See an overview of Norwegian jøkulhlaups here.

Jøkulhlaups in Norway in recent years

  • Øvre Messingmalmvatnet at Rundvassbreen, Blåmannsisen in Sørfold, Nordland - first time in 2001, then in 2005, 2007, 2009, 2010, 2014 and 2016.
  • Demmevatnet at Hardangerjøkulen in Eidfjord, Hordaland - 2014, 2016 (2 events).
  • Tystigbreen in Stryn - 2014.
  • Koppangsbreen in Lyngen - first time in 2010, then in 2011, 2012 ( 2 events), 2013 (9 events), last 2014. 
  • Harbardsbreen in Luster, Sogn og Fjordane - since 1994, recently in 2010, 2012 (small) and 2015.
  • Flatbrevatnet at Flatbreen, Jostedalsbreen in Sogndal, Sogn og Fjordane - 2004.
  • Øvre Svartanutvatnet at Søndre Folgefonn in Odda, Hordaland - 2002.