AQA · A-Level · Geography
Course version: 7037 · Version from Sept 2018
Systems and processes: Glacial systems including glacial budgets.
A glacier operates as an open system driven by climate.
Checked against the AQA 7037 specification (opens in a new tab) on .
- Point 1 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A glacier operates as an open system driven by climate. Inputs (accumulation) primarily include snowfall, avalanches, and wind deposition, adding mass to the upper glacier. Outputs (ablation) involve melting, calving, and sublimation, removing mass at the snout. The glacial budget, or mass balance, is the annual difference between total accumulation and total ablation. If accumulation exceeds ablation, the budget is positive, and the glacier advances. Conversely, a negative budget causes retreat.
For example: The Rhone Glacier in Switzerland currently exhibits a strongly negative mass balance, losing significant volume (measured in m³ of water equivalent) annually due to rising global temperatures, leading to rapid snout retreat.
What earns the marks
- Identify glaciers as open systems with inputs (accumulation), stores (ice mass), transfers (ice movement), and outputs (ablation).
- Define the glacial budget (mass balance) as the net difference between accumulation and ablation over a one-year period.
- Explain the concept of the equilibrium line, where annual accumulation exactly equals annual ablation.
- Relate a positive mass balance to glacial advance and a negative mass balance to glacial retreat, linking this to climate change.
Common mistakes and how to put them right
Stating that a retreating glacier moves backwards.
Put it right by explaining that the ice always flows downhill under gravity, but the snout melts faster than ice is replenished.
Confusing accumulation with advance.
Put it right by noting accumulation is an input process (e.g., snowfall), whereas advance is the physical extension of the snout due to a positive budget.
Ignoring sublimation as an output.
Put it right by including sublimation (direct phase change from solid ice to water vapour) alongside melting and calving in ablation zones.
Exam tips
- Draw and label a systems diagram showing inputs, the equilibrium line, and outputs to support explanations of glacial budgets.
- Use the term 'water equivalent' when discussing changes in glacial mass or volume.
- Reference a specific, named glacier (e.g., Mer de Glace) when discussing recent trends in negative glacial budgets.
Try the lesson
The start of the Systems and processes: Glacial systems including glacial budgets. lesson, made from checked teaching notes for this specification point.
Have a go first
In a glacial system, which of the following represents the primary components of the glacial budget?
Listen
A glacier operates as an open system driven by climate. Inputs (accumulation) primarily include snowfall, avalanches, and wind deposition, adding mass to the upper glacier. Outputs (ablation) involve melting, calving, and sublimation, removing mass at the snout. The glacial budget, or mass balance, is the annual difference between total accumulation and total ablation. If accumulation exceeds ablation, the budget is positive, and the glacier advances. Conversely, a negative budget causes retreat. For example, the Rhone Glacier in Switzerland currently exhibits a strongly negative mass balance, losing significant volume (measured in m³ of water equivalent) annually due to rising global temperatures, leading to rapid snout retreat. A strong answer earns marks for these points. Identify glaciers as open systems with inputs (accumulation), stores (ice mass), transfers (ice movement), and outputs (ablation). Define the glacial budget (mass balance) as the net difference between accumulation and ablation over a one-year period. Explain the concept of the equilibrium line, where annual accumulation exactly equals annual ablation. Relate a positive mass balance to glacial advance and a negative mass balance to glacial retreat, linking this to climate change. A common slip: Stating that a retreating glacier moves backwards. Instead, explaining that the ice always flows downhill under gravity, but the snout melts faster than ice is replenished. Exam tip: Draw and label a systems diagram showing inputs, the equilibrium line, and outputs to support explanations of glacial budgets.
Key words
Say what each word means before you turn the card.
Systems theory
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Mass balance
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Climate change impacts
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Glacial dynamics
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See every definition
- Systems theory
- Glaciers are open systems with inputs, stores, transfers and outputs.
- Mass balance
- The annual difference between total accumulation and total ablation, also called the glacial budget.
- Climate change impacts
- Rising global temperatures cause a strongly negative mass balance, losing volume annually and leading to rapid snout retreat.
- Glacial dynamics
- A positive budget causes the glacier to advance, while a negative budget causes retreat.
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