Glacial Motion : Flow Surge Glaciers

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Glacial Motion Flow Surge Glaciers A
facilitation by Tom Beers
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Surge Glaciers

• Surge glaciers can increase velocities by two
  orders of magnitude
• -Columbia, 35 m/day
• -Variegated, 50 m/day, kinematic waves 250- 400
  m/hr
• High concentrations found in Svalbard, Canadian
  Arctic islands, and Alaska

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Surging Glaciers

• First Record 1620 Dutch Map Recherchebreen
• Surge phases
• - 5-10 years in Svalbard
• - 1-3 years in North America
• Svalbard
• -2100 Glaciers, 86 known to surge
• -Brasvellbreen, 20 km advance - 30 km front

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Svalbard, Norway
Figure 1.-The location of Svalbard, the islands
that make up the archipelago, the areas covered
by glaciers, and the glaciers mentioned in the
text. Base map courtesy of Norsk Oslo. The
glaciers are indicated in white. (See fig. 4 for
cross section.)
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Surging of Antarctic / Laurentide?

• Antarctic (Hollin, 1969)
• -Rapid sea level rise 17 m
• -Pollen and mollusc record
• -No sediment evidence of surge around Antarctic
  found yet
• -Suggested by some to cause Pleistocene Ice ages
• Laurentide via Hudson Strait ice stream
• -Ocean cores show advances and advanced calving
• -Binge purge cycles
• -Critical ice thickness

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Surge, Retreat, Renewal

Surges of Fridtjovbreen Glacier (Lonne)
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Trapridge Glacier, Yukon Territory

• -1969 - 2005 monitored extensively
• -Complete Surge cycle (1951-2005)
• -Increased from 14.7m/yr to 41.8m/yr

(Clarke, et al.)
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TOM-PIERRE FRAPPÉ-SÉNÉCLAUZE, 2002
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June 1980, Clarke
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Cold / Warm Bed Interface

• 17 Holes drilled
• Reservoir area pressure melting point, -0.05 C
• -Shear stress reduced
• -Increases in slope and thickness
• Receiving area frozen to the bed, -1.77 C
• -stagnate and even thinning
• 40 meter bulge forms at the interface

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Observations

• Bulge site 10X normal geothermal heat
• -Runaway strain heating?
• Receiving area Highly fractured volcanics and
  low grade metamorphosed Carbonates
• Site 11 Subglacial water system is hit while
  drilling
• Abnormal heat subglacial water percolating
  through unfrozen substrate beneath permafrost

Clarke et. Al 1983
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Theories

• Rothlisberger 1969
• -The sub-glacial drainage system is destroyed at
  the onset of a surge
• Clarke et al. 1983
• -we take this idea a step further and suggest
  that destruction of the subglacial drainage
  system is the event that triggers a surge.
• -competition between construction and
  destruction

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Variegated Glacier, AK

• -Many surges
• -Observed periodically since 1895
• -Average quiescent phase 13-18 years
• -Maximum velocity 50 m/day (1982 -1983)

Surging phases since 1900 (Eisen et. Al 2001)
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1982-1983 Surge

• Demonstrated two phases of surge
• -Both peaking in June
• Periods of kinematic waves
• - showed increased basal water pressure
• -increased ice velocities
• -terminating in blowouts of water in outlet
  streams

(Kamb et al. 1985)
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Velocities
(Kamb et al. 1985)
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Water Depth
(Kamb et al. 1985)
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Basal Water Pressure vs. Velocity
(Kamb et al. 1985)
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Kamb's Mechanisms

• Late melt-season
• -Insufficient water flux to sustain a normal
  tunnel system
• Winter
• -high water pressures built
• -Interconnected cavity system developed
• -sustained via rapid sliding
• FLOATING GLACIER!

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• Questions?