Controls Snow & Ice Distribution
1. Climate
A) Precipitation
B) Temperature
2. Latitude
/ Altitude
3. Relief & Aspect
- Continentality
Climate favouring glaciation
Cold temps, esp summer (prevents melt)
Lotsa snow buildup (snow precip
High proportion precipitation = snow
favours glaciation
Caveat
If low melt rates, ice may buildup
Despite absolute low snowfall per annum
e.g. Arid interiors of large ice sheets
Cooler temperatures - promote greater ice extent
∴ Glaciers generally exist where mean annual air temp < 0°C
Complexity temp influence snow/ice
Mean summer temp dictates ice preservation
Glacial tscale control ice extent
Orbital eccentricity & 100 kyr cycle
Controls ice extent i.e. buildup on glacial timescales
High latitudes preferred for glaciation
due to low (negative) net solar radiation
∴ Higher latitude --> lower snowline altitude
Snowline
= elevation snow exists @ end of summer
Glaciers @ low latitudes
Only occur @ high altitudes e.g. Kilimanjaro
Altitude - influences temp & precipitation
can be influenced by local temp ∆ (depressed/raised)
Snowline Trends
Generally snowline altitude increases toward Equator
Exception
Snowline depressed either side of Equator (~30°N & S)
due to precipitation control i.e. lotsa rain in subtropics
Alps snowline
= getting higher (altitude increasing) over past century with warming temps
Relief
Presence of land
= required for glacial ice growth
- Arctic ocean - little land ∴ seaice
- Antarctic - continent ∴ ice sheet
Local topography
constrains ice extent via pinning points
e.g. Antarctic ice shelves
Aspect
= Orientation of land surface wrt incoming solar radiation
pinning pts allows ice growth beyond land margin
Local effects on ice buildup via influences on precip & temp
N facing slopes
more likely to develop ice as shaded
Precipitation
= influenced by topog on range of scales
e.g. Loch Lomond Stadial ice cap
Ice dominated W Scotland
Prevailing winds brought snow to W ~ 11-12 kyr
∴ Rainshadow effect starved E coast of snow
--> hence minimal ice cover despite colder temps on E vs W
= Distance from ocean
Influences accumulation vs ablation signif on major ice sheets
However, regional oceanic/atmos circulation patterns are also critical
Further from moisture source - lower accumulation
Accumulation Pattern on IS
AIS
Highest accumulation - margins
Warmer & open ocean(less sea ice)
∴ more moisture in air
Drier near interior
few mm/yr water equivalent
Especially West Antarctic Peninsula
GrIS
Demonstrates variability
Accumulation higher in South (& margins?)
Mid-lat Westerlies bring more precipitation to S
Thermohaline circulation delivers warm water near S Greenland