Ice Mushrooms of the Patagonian Andesdynamics/materhorn/PDF/DACA_talk... · 2017-04-06 · • Rime...
Transcript of Ice Mushrooms of the Patagonian Andesdynamics/materhorn/PDF/DACA_talk... · 2017-04-06 · • Rime...
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Ice Mushrooms of the Patagonian Andes
C. David WhitemanUniversity of Utah
Rolando GaribottiChalten, Argentina
Cerro Torre, Argentina DACA 2013, Davos, Switzerland, 9 July 2013
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Cerro Torre massif
Torre Egger
Cerro Standhardt
Cerro Torre
Punta Herron
Rolando Garibotti
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© Jorge Ackermann
Torre Egger
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© Rolando Garibotti
Paine Grande SW
Rime mushrooms can present a significant impediment to mountain climbers.
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© Rolando Garibotti
Ragni Route
Ragni Route
El Arca de los Vientos
Two views of Cerro Torre 3128 m
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Cerro StandhardtN Ridge
© Rolando Garibotti
30 m
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Monte Sarmiento,Tierra del Fuego
© Ralf Gantzhorn
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© Ralf Gantzhorn
Cerro San Lorenzo
In 2000 Toni Rohrer (Switzerland) and Santiago Batet (Argentina) lost their lives when the summit mushroom of Cerro San Lorenzo collapsed
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Monte Sarmiento, Tierra del Fuego
© Ralf Gantzhorn
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© Rolando Garibotti
Punta Herron W Ridge
Ice mushrooms form on this ridge. They grow and then break off.
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Rime mushroom: A bulge, mound or mushroom-shaped projection of ice produced primarily by the accretion of hard rime on a surface-based obstacle such as a summit, ridge or mountain face, lasting more than one year, and constituting an obstacle to climbing.
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RimeType Characteristics Mode Adhesion T (°C)
SoftFragile rime consisting mainly of thin needles or scales of ice, density ~0.2 g cm-3
Deposition of vapor in solid form from super-cooled fog, or air super-saturated with respect to ice. Fog not essential.
Easily detached < -8
Hard
White granular structure with crystalline branches of ice grains more or less separated by entrapped air. Deposit grows upwind, density ~0.5 g cm-3
Fog essential. Rapid freezing of super-cooled fog droplets, leaving interstices. Moderate or strong winds
Rather adhesive but can be scratched off
-2 to -10
Clear
Amorphous compact ice with alternate transparent and opaque (bubbles of air) layers, density ~0.8 g cm-3
Slow freezing of fog drops with released heat hindering crystallization
Firmly adheres to surface
0 to -3
WMO (1975)Compare glaze
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Hard rime: white ice that forms when super-cooled cloud droplets freeze on the windward side of sub-freezing ground-based obstacles, usually with high wind velocities and air temperatures between -2 and -10°C. WMO (1975)
Hard rime
note the ‘overhang’
hard rimewind speed
Makkonen and Lozowski (2008)
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dM/dt = w U A [kg s-1]
M = mass of accretion of S-C dropletst = timew = liquid water contentU = wind speed normal to surfaceA = surface area = collision coefficient (0 - 1)
Rate of accretion of super-cooled liquid water mass on a sub-freezing structure:
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Collision efficiency = 1
Collision efficiencySkiing analogy
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Accounts of Ice or rime Mushrooms
• American Alpine Journal, 1929-present
• Personal accounts of climbers
• Web search
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Reports of permanent rime mushroomsAAJ, 1929-present, “funghi di ghiaccio” 1959; eispilzen; Hongo de hielo
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Meteorology of Rime Mushrooms -
Patagonia
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January July
Wind speed (m s-1) Wind speed (m s-1)
70 kPa
ERA interim reanalysis
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PM = Puerto MonttCR = Comodoro RivadaviaCT = Cerro TorrePA = Punta Arenas
Radiosondes 1975 -Apr 2012
Google mapsNCDC: Global radosonde archive
Southern Patagonian
Ice Cap
Northern Patagonian
Ice Cap
Cerro Torre is in the Monte FitzRoy Massif
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70 kPa winds
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Lifting condensation level
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Height of -2° and -10°C isotherms
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Climbing Ice Mushrooms
anchorage, surface characteristics and internal cohesion
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“Oh, hey! I just love these things! …Crunchy on the
outside and soft on the inside!”
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© Bjørn-Eivind Årtun
Torre Egger
Anchorage
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Punta Herron
© Hayden KennedyFitzRoy Massif in background
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© Ralf Gantzhorn Monte Sarmiento
Surface characteristics
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© Rolando Garibotti
Cerro Torre
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© Bjørn-Eivind Årtun - Ole Lied
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© Rolando Garibotti
Natural tunnels Cerro Torre W Face
W Face Cerro Torre natural tunnel was climbable 2005-2008+. Absent in 2011.Reports of such tunnels date back to mid-1980s.
Colin Haley entering 50-m long natural tunnel
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50 m long natural mushroom tunnelW face Cerro Torre
A similar tunnel was climbed on Torre Egger in 1993 by Jay Smith and partners
© Bjørn-Eivind Årtun
This tunnel climbable from 2005 through at least 2008. No longer present in 2011-2012.
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© Rolando Garibotti
Cerro TorreSummit mushroom
2008, Colin Haley digging tunnel, 4 hours for 30 m.
2008, Colin Haley finishing tunnel
© Rolando Garibotti
Internal cohesion
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© Rolando Garibotti
Jorge Ackermann digging upper part of a tunnel/half pipe in CT’s last mushroom
Cerro Torre 6 climbers
© Cullen Kirk
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© Colin HaleyTorre Egger
January 2012 Hazards
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© Colin Haley
Cerro Torre
climbers
January 2012
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topography cloud microphysics airflow dynamics
ice mushroomssynoptic, seasonal and
interannual effects
internal
external
ice metamorphism
crustsphase changescollapses
distance to ocean
SST
terrain relief
local vertical motions
terrain channels
isolated peaks
topology -ridges, summits
firmament-attachment
aerosol spectrum
droplet size distribution
cloud formation
hard rime
other hydrometeors
phase changes
windward accretion
large-scale vertical motions
wakes
turbulence
wind channeling
tunnel formation
Why grow upwind? overhang? grow vertically?
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Summary
Acknowledgments: UU: Wesley Harrison, Matt Jeglum, Jeff Massey. NCAR: Kevin Trenberth and Dennis Shea. Climbers: Camilo Rada, Ralf Gantzhorn, Colin Haley, Gregory Crouch, Simon Garrod, Jorge Ackermann, Damien Gildea, Simón Elías, Hayden Kennedy, Ole Lied, Bjørn-Eivind Årtun and Lionel Daudet.
• Rime mushroom examples and definition• Physics: super-cooled cloud droplets and strong winds• Global locations of reports• S. Patagonia - a favored location for rime mushrooms
• Extremely strong, consistently westerly winds• High frequency of clouds with low bases• High frequency of super-cooled cloud droplets
• Examples of obstacles to mountain climbing• Texture, internal cohesion and anchorage• Half-pipes and natural tunnels
© CD Whiteman38