G - Glacial Systems

Definitions - Flow diagrams

System:

A set of interconnected parts that work together. They have a series of stores and components that have flows between them.

Open system:

Matter can be transferred into and out of the system.

Closed system:

Energy can be transferred in and out, but matter cannot.

What are the inputs in a glacier system?

The input is snow.

What are the outputs in a glacier system?

The outputs are melt-water and moraine, as well as icebergs from calving.

Mass balance:

The balance of mass through the glacier. This can affect the movement of the glacier.

Equilibrium:

When the inputs and outputs in a system are balanced, it is in equilibrium.

Positive feedback loop:

When the effects of an action are amplified by changes, so the process increases and continues.

Give an example of a positive feedback loop:

- Ice expands, causing higher albedo
- More insolation is reflected
- Temperatures decrease
- Further growth of ice sheet, cycle repeats.

Negative feedback loop:

When the effects of an action are nullified by change, returning the system to equilibrium.

Give an example of a negative feedback loop:

- Melting ice exposed land
- More plants survive and have longer growing seasons
- Plants sequester more CO2, reducing the greenhouse effect
- Less melting of ice, cycle ends.

Glacial budget:

The total accumulation and ablation in a glacier.

Firn line:

Above this line, snowfall accumulates in the glacier. Below it, snowfall will melt.

Accumulation:

The build-up of precipitation in a glacier. Net accumulation is the material left over at the end of the melt season.

Accumulation area:

Where accumulation occurs.

Ablation:

The process of wastage of snow or ice by melting, sublimation, and calving.

Ablation area:

Where ablation exceeds accumulation.

Equilibrium line:

Where a year's ablation balances a year's accumulation. Determined at the end of the melt season, and is often close to the firn line.