Linkage between General Climate & Glacier snout behaviour
Factors controlling glacier response over time
Relaxation/ response time – time interval between change of input & the achievement of new equilibrium
Amplification factor – small change in mass balance initiate large change at the glacier terminus
Specific mass balance characteristics – damp down minor climatic oscillations
Steady state situation – glacier remain at zero for many years & glacier dimension remains constant
Glacier Morphology
Response to climate
Distance between snout & accumulation Area – contributes to fluctuations due to climate
Narrow valley glacier – more time to respond than ice cap
On Land – Glacier Responds by expanding/ withdrawing snout
Extension – more surface area exposed to ablation
Fjord – difficulty in achieving equilibrium, continue to advance until spread out & increase cross sectional area exposed to melting & calving
Mass Balance Changes
Minor oscillations – direct response to annual climate oscillations
Major advances/ retreats – indirect/ lagged, significant long term changes
Direct response – short term mass balance change
Negative mass balance – reflected in 1 season
Positive mass balance change – may not be reflected by several seasons
Climatically induced snout retreats – more rapidly than climatically induced snout advances
High Accumulation, Low Ablation – interrupts retreat
Glacier Activity – influences velocity of kinematic waves
Very active Glaciers (Western Side of New Zealand) – responds directly to climatic oscillations
Sluggish glaciers (eastern side) – greater time lag
Compute response tie of Glaciers (e.g. Berendon Glacier in British Columbia by Nye)
Glacier Length
Height of Glacier Surface above mean sea level
Slope of surface
Mass Balance data
Mathematical models – Assumes
- Climatic fluctuations are small
- Any effects caused by changes in the quantity of melt water at the base can be ignored
- Changes in the temperature of ice (and thus the relation of stress to strain rate) can be ignored
Glacier mass balance change – measureable
Predictable
Surge behaviour
Surge – snout advance
Have a cycle of activity
Not climatically induced
Prolonged storage of surplus mass – until critical stage of instability or threshold reached
Attainment of critical stage is predictable
Wavelength & amplitude of surge cycle – shorter for small valley glaciers
Variations over days & weeks – related to ablation rates & meltwater discharge
Short-lived advances interrupting overall period of retreat – rapid responses to minor climatic oscillations
Little ice Age – 1500 -1920
Alpine climatic fluctuations from
Records of vineyards
Fruit growing, settlement history
Cereal growing, ease of ocean travel aspect of individual dated settlement sites
Vegetation studies – pollen analysis, lichenometry, studies of changing tree-line altitude------information on climatic fluctuation
Archaelogical & pedological investigation – information on recent climatic fluctuations
Technique – radio – carbon dating
Indicator of severity of Icelandic climate – sea ice off Icelandic coasts
Radiometric dating, palynology, dendrochronology….lichnometric technique
Prediction of glacier Behaviour – numerical model experiments of Climap Project, NCAR project
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