Axel Heiberg Island, Canada
Hva er en isbre ? Hvorfor beveger isbreene seg ? Isbre = snø og ismasse i bevegelse Isen er deformerbar – ”brød-deigen” Isen endrer egenskaper med trykket (istykkelsen) Isen glir
Folgefonna
Alaska – flytbevegelse - midtmorener
Surface velocity us is partly caused by gliding ug and partly deformation ud Gliding/sliding varies considerably – deformation is almost constant (depending on slope and thickness) us = ug + ud
Sprekker på breer i Norge – Svalbard - Antarktis 50 m
Bondhusbreen, Folgefonna
Bondhusbreen - Folgefonna
Helikopter- platform Bondhusbreen
Bondhusbreen - tunnellsystem Tunnellsystemet under Bondhusbreen Bondhusbreen - tunnellsystem
Isen deformeres
Isen deformeres
Is er en seig masse som endrer egenskaper med trykk og temperatur Glens flow law - deformation of ice: Liquids:
Deformation rate h = 160m Glens flow law: ė = A τⁿ Closure rate: dr/dt = A (P/n)ⁿ dr/dt ~ 100-150 mm/d If P = ρgh = 14 bar, n = 3: A = 0.36 y-1 bar-1 or 11.4 * 10-15 s-1kPa-3 - twice as high as Peterson
Nigardsbreen still advanced in 2004
Artificial roche moutonne (Rundsva) with a boulder in the ice
Boulder crossing
Rock wall pressures - water opening- temperatures
Rock crushing Ice Rock
Hvordan eroderer breene ? Skuring Knusing Plukking Erosjon – transport – avsetning
Rundsva
Skuring, brunhud, plukking Svenske skjærgården
Plucking