Online Diary

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

Saturday, August 15, 2009

Spatial Distribution of Glaciers

Current glacierization
Areal Extent of Glaciers

Flint: - Importance of knowledge of Glacier Volumns – appreciate the importance of glacierization

Glacier volume – by radio-echo sounding
Degree of Inundation of land surface by snow & ice
Degree of Glacierization – percentage of land surface covered at the end of Balance
Year,
Data Plotted on a grid instead of a map
Degree of relief by ice
- Morphological variable within a landscape system
- Index of the intensity or type of glacial or nival processes operating upon the bedrock base

Detailed movement of snow & ice thickness – radio echo sounding profile
Continuous data concerning ice surface altitude & form, ice thickness, sub-ice bedrock relief
Applied in Greenland, Arctic Canada & Antarctica

Factors influencing the current distribution of snow & ice
Precipitation
High Evaporation rate, low annual precipitation, negative net precipitation
High altitude west coast environment – extremely heavy precipitation
Glaciologically influence as precipitation in the form of rainfall – contributes little to glacier mass

Nivometric coefficient – index of snow effectiveness
- ratio of snowfall (in water equivalent) to total annual precipitation

Nivometric coefficient – > 1 low precipitation
less suitable for glacial growth suitable for prolonged glacial survival

Medium Nivometric coefficient – high precipitation
Marginal from point of view of glacierization

Nivometric coefficient < 1 – high precipitation

Temperature
Mean summer temperature
Relationship between regional temperature characteristics & glaciarization

Latitute
Ice cover zone
Frost rubble zone climatically contolled systems
Tundra Zone

Altitude
Independent parameter at regional & local scale. Fundamental control over climatic parameters & hence on glacier distribution
Altitudinal zonation of mountainous area
Glacial/ Nival
Sub nival
Alpine
Sub Alpine
Upto sea level in high laltitude
High altitude in low latitude

Relief
Surface relief
Breath of an individual summit determines whether or not a glacier can be supported
Glaciation level
Partsch – brucker method of defining this limit

Snow fence effect – jaggered mountain scenary in baffin island in trapping snow &
allowing cirque glacier to develop lower than normal altitudes
mass balance – position of snout
morphology of channel – precise location of channel

shape ratio: ratio of elevation to area – and over 600m
roughness index: geometric properties of surface
high dissected topography – inhibit glacierization

Aspect
Orientation of ground surface with respect to incoming solar radiation (local scale)
Little control at regional/ larger scales

Distance from nearest ocean
Independent variable – influencing
Regression analysis

Glacier Inertia
Ice caps & ice sheets – out of equilibrium with their climatic environment devoid of relationship between morphological parameters as altitude, aspect & relief

Regression graphs are used to pot relationships – eg . Between altitude of glaciations level for Norway & ocean distance – Chorlton & lister