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Haut Glacier d'Arolla 2 (Two-component drainage (Residual…
Haut Glacier d'Arolla 2
Two-component drainage
Residual hydraulically inefficient drainage
Will remain
above snowline in
accumulation area / btwn moulin
Moulin & channels route
most surface meltwater
= hydraulically efficient
∴ Percolation still occurs in between
--> drains small inputs from crevasses / geothermal basal melt
Implications drainage evo
Inefficient drainage
Meltwater routed
slowly
to channels/terminus
High contact btwn meltwater & glacier bed
[Config @ start melt season]
Acquires lotsa solutes
Efficient drainage
Melt
routed
rapidly to glacier terminus
Shorter travel time
Much less contact btwn meltwater & bed
∴ Lower solute conc
(higher water quality)
PhD Conclusions
Glacier = underlain by dynamic 2 component subglacial drainage system
Efficient
channelised drainage system
evolves upglacier during melt season
--> As snowline retreats &
surface melt inputs to moulins increase
Subglacial water pressure
Gordon (1998)
Borehole water level variations
Indicate subglacial water pressure changes
As melt season progresses
Up til ~end July - Higher water pressure
After July
Lower water pressure
More pronounced diurnal cycles
Velocity tracks water pressure variation
Evo Borehole Water Pressure
Beginning season
Snowpack present, melting
High water pressure
Later in season - channelised drainage developed
Drop in pressure
Pronounced diurnal pressure variation
Reflects daily variation melt input
(Melt input in morn)
Diurnal Pressure Variability
Concurs with diurnal velocity variability
Glacier runoff
Early - little
Water from slow snowpack melt/geothermal (~ 1 cumec)
June - Increasing
Supraglacial melt --> increase
Snowfall removal --> decrease
Later - stronger diurnal cycle
Snowpack removed
6 - 8 cumecs