Jökulhlaup

A jökulhlaup (or glacier burst) is a subglacial outburst flood. It is an Icelandic term that has been adapted into the English language. It originally referred to the well-known subglacial outburst floods from Vatnajökull, which are triggered by a volcanic subglacial eruption, but now is accepted to describe any abrupt and large release of water from a subglacial lake. It is thus a special case of glacial lake outburst flood, together with marginal lake drainages.

Since jökulhlaups emerge from hydrostatically sealed lakes with floating levels far above the threshold, their peak discharge can be much larger than that of a marginal or extra-marginal lake burst. The hydrograph of a jökulhlaup from Vatnajökull typically either climbs during weeks with the largest flow near the end, or it climbs much faster during the course of hours. This is suggested to reflect channel melting, and sheet flow under the front, respectively. [Björnsson 2002]

Jökulhlaups are usually associated with Vatnajökull, Iceland. They have, however, been observed indirectly under the Antarctic at present, and it has been suggested that they also occurred from the Laurentian ice sheet [Shaw 1983] [Beaney and Shaw 2000] [Alley et al. 2005] [Erlingsson 2008] and the Scandinavian ice sheet [Erlingsson 1994] during the last ice age.

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*Beaney, C. L. and Shaw, J., (2000). The subglacial geomorphology of southeast Alberta: evidence for subglacial meltwater erosion. Can. J. Earth Sci., 37:51-61.
*Björnsson, H., (2002). Subglacial lakes and jökulhlaups in Iceland. Global and Planetary Change, 35:255–271.
*Alley, R.B., Dupont, T.K., Parizek, B.R., Anandakrishnan, S., Lawson, D.E., Larson, G.J. and Evenson, E.B., (2005). Outburst flooding and the initiation of ice-stream surges in response to climatic cooling: A hypothesis. Geomorphology, 75: 76-89.
*Erlingsson, U., (1994). The ‘Captured Ice Shelf’ hypothesis and its applicability to the Weichselian glaciation. Geogr. Ann., 76A (1–2): 1–12.
*Erlingsson, U., (2008). A jökulhlaup from a Laurentian captured ice shelf to the Gulf of Mexico could have caused the Bølling warming. Geogr. Ann., 90 A (2): 125-140.
*Shaw, J., (1983). Drumlin formation related to inverted melt-water erosional marks. J. Glaciol., 29:461–479.