Glaciers 1

What are some key reasons to study glaciers

• sea level rise

• the economy

• ecology

• hazards/slope stability

• irrigation

• civil engineering

• cultural significance

What are the climate factors influencing glaciers?

• solar radiation

• latitude

• altitude

• precipitation

How does altitude influence glaciers?

• as altitude increases, precipitation increases and temperature decreases

• cold air holds less moisture, so releases it

• low temperature means precipitation as snow more likely

What is the solar radiation effect and how does it relate to glaciers?

• the way in which solar radiation circulates effects the earth’s surface temperature

• polar locations are ideal for ice build-up due to large land + consistent high snowfall

Describe a glaciers mass?

• a natural open system

• made of accumulated crystalline water

• snow becomes ice when snowpack/glacier density increases

• firn - old snow, atleast a year old

Dry vs Wet snow?

• Dry - requires more snow to form ice

• Wet - easier to form ice as water trickles down into the ice pack and freezes

• presence of meltwater = increased rate of ice formation and metamorphism

What is Glacier mass balance/mass budget?

o   Quantative expression of the volumetric change that ice mass expiernces

o   Describes the inputs and outputs of snow, firn and ice at various spatial and temporal scales

o   Can help us understand the objective ‘health’ of a glacier and the impact of climate change

What is glacier mass ablation?

when ice bodies lose mass as a response to temperature, pressure and humidity changes

What are the factors affecting ablation?

• altitude - decreases with increased altitude

• wind - impacts turbulent heat flux

• cleanness of snow - albedo is higher in clean winter snow and lower in dirty summer snow(0.9 vs 0.3)

• calving - when large chunks break off ice bodies (ice sheets/shelves)

• sublimation - occurs are lower temperatures with strong winds, intense sunlight and very low air pressure

• surface melting

• internal and basal melting - mass lost by water flow

What is the Equilibrium Line Altitude(ELA)?

• the boundary between ice and snow at the surface at the end of melt season

• The altitude at which there is no net annual gain or loss of ice body mass is key for monitoring mass balance

What is the Glacial net balance

• Reflects the difference between accumulation(gain) and ablation(loss) usually for a whole glacier over one year

•   Net balance usually calculated over a balance year, end of summer to end of summer

• Can be calculated over measurement year defined by fixed calander dates

•   Measures in units of equivalent volumes of water per unit area

• Net balance = the difference between the winter balance and summer balance

What can mass balance tell us?

• Information about glacier advance or retreat

• Glacier flowàhigh accumulation = high flow rate, low accumulation = low flow rate

• Flow allows mass to be transferred from accumulation area to the ablation area

What do global patterns in the net balance value show?

a global pattern of increasing negative net balance(glacier retreat)

Continental vs maritime type glaciers

• continental-type glacieràlow accumulation, low ablation = low balance gradient(e.g major ice sheets, high Arctic glaciers)

• maritime-type glacieràhigh accumulation, high ablation = high balance gradient(e.g southern alps, new zealand, European alps)