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Glacial Lake Outburst Floods (Possible Origin (Ice marginal / proglacial…
Glacial Lake Outburst Floods
What?
= Extreme / unusual & rare glacial flood events
Possible Origin
Ice marginal / proglacial lakes
Subglacial lakes / subglacially-stored water
Supraglacial lakes
Extreme rainfall events
Rapid surface melting
-
Greenland 2012 anomaly
Recurrence interval varies
∴ Hard to predict
Depends on mechanism driving flood
Importance GLOF Study
Rep signif hazard
Himalaya
Especially big risk to life
Iceland
Recognised as danger for centuries
∴ Better at monitoring / evacuation
Implications
Erosion / sediment flushing
signif
Dynamics (flow velocities)
Subglacial condition
Glacial hydrology
Huge volumes meltwater produced
Glacial systems where lakes flood
Proglacial lakes
lakes dammed behind terminal moraines
Ice marginal lakes
@ glacier sides
Subglacial lakes
beneath / within glacier
Supraglacial lakes
on glacier surface
1. Proglacial lakes
Dangerous
- moraine dam =
unstable
Collapse / GLOF may result from
Dam collapse
Lake overtopping moraine
i.e. Huarez, Peru 1941 - glacier ice fell into lake initiating a flood wave
Mitigation
monitoring & warning systems being developed
Difficult to predict
drainage occurs rapidly due to vast water volumes
Lakes 'impounded' / dammed behind proglacial moraine (lateral or terminal)
2. Ice marginal lakes
= Lake dammed along edge of glaciers
Dammed by
glacial ice
Water drains from ice surface --> impounded by marginal ice cliff
Can be v large -
up to 500 - 1000 cumecs melt water !
Subglacial lakes
Distribution
V common beneath Antarctica
Some found beneath Greenland
Hazard
Ice sheets
Drainage not normally hazardous
Iceland
Poses signif danger
Significance
Microbial life @ lake bed e.g. Lake Vostok
Extreme envmts & aphotic
Formation
Geoethermal heating and/or subglacial eruptions
Most dramatic GLOFs