Key idea: the amount of ice depends on the glacial budget. This has seen a loss since 1850 and there are seasonal changes due to temperature fluctuations

Objectives: Glacial budget – accumulation and ablation, advance and retreat Seasonal shifts in temperature and glaciers

Glacial budget – accumulation and ablation, advance and retreat

Seasonal shifts in temperature and glaciers

The glacier system A glacier behaves as a system. It has inputs, stores, flows and outputs

A glacier behaves as a system. It has inputs, stores, flows and outputs

INPUT Precipitation – falling snow in the zone of accumulation , from avalanches or directly onto the glacier During fresh snow falls air is trapped between the flakes. Under pressure individual particles of ice melt around their edges allowing air to escape. One by one the particles slip forward on the thin film of water and immediately refreeze. In this way the ice of a glacier moves slowly forward in plastic flow at a speed of about 300m per year

INPUT

Precipitation – falling snow in the zone of accumulation , from avalanches or directly onto the glacier

During fresh snow falls air is trapped between the flakes.

Under pressure individual particles of ice melt around their edges allowing air to escape. One by one the particles slip forward on the thin film of water and immediately refreeze. In this way the ice of a glacier moves slowly forward in plastic flow at a speed of about 300m per year

Stores – the glacier is a store of water Transfers - As more snow falls the underlying layers are compressed into ice. One by one the particles slip forward on the thin film of water and immediately refreeze. In this way the ice of a glacier moves slowly forward under the force of gravity. Outputs – outputs from the system is meltwater with a small amount of evaporation. Ablation is the melting of a glacier.

Stores – the glacier is a store of water

Transfers - As more snow falls the underlying layers are compressed into ice. One by one the particles slip forward on the thin film of water and immediately refreeze. In this way the ice of a glacier moves slowly forward under the force of gravity.

Outputs – outputs from the system is meltwater with a small amount of evaporation. Ablation is the melting of a glacier.

OUTPUTS Output from the system is mainly in the form of meltwater with a little bit of evaporation When a glacier melts it is called ablation . Accumulation is greater than ablation near the head of a glacier in winter. Ablation will exceed accumulation in summer when the temperatures are warmer. If ablation exceeds accumulation then the glacier will melt If accumulation exceeds ablation then the glacier will extend .

OUTPUTS

Output from the system is mainly in the form of meltwater with a little bit of evaporation

When a glacier melts it is called ablation .

Accumulation is greater than ablation near the head of a glacier in winter.

Ablation will exceed accumulation in summer when the temperatures are warmer.

If ablation exceeds accumulation then the glacier will melt

If accumulation exceeds ablation then the glacier will extend .

Tasks Copy the diagram of the glacier system Write a sentence to explain why the glacier is described as a system – what are the inputs, stores, transfers, outputs. What is meant by ablation and accumulation When and where is accumulation highest? When and where is ablation highest? What evidence is there that glaciers are retreating? What is the suggested cause?

Copy the diagram of the glacier system

Write a sentence to explain why the glacier is described as a system – what are the inputs, stores, transfers, outputs.

What is meant by ablation and accumulation

When and where is accumulation highest?

When and where is ablation highest?

What evidence is there that glaciers are retreating? What is the suggested cause?

http://news.bbc.co.uk/player/nol/newsid_4630000/newsid_4635400/4635465.stm?bw=bb&mp=wm&news=1&bbcws=1

http://news.bbc.co.uk/player/nol/newsid_4630000/newsid_4635400/4635465.stm?bw=bb&mp=wm&news=1&bbcws=1