2.3.1

Mass Balance

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Inputs and Outputs of Glacial Systems

Glaciers operate as a system with inputs (accumulation) and outputs (ablation) and both influence the mass balance of a glacier.

Inputs (accumulation)

Inputs (accumulation)

  • Direct snowfall and other forms of precipitation.
  • Meltwater from melting snow and ice that re-freezes.
  • Rock fragments that have fallen on to the glacier or been eroded by it.
  • Avalanches of snow and/or rock, and wind-blown deposits.
  • Solar energy. But, snow and ice have a high albedo meaning much radiation is reflected (up to 90%).
Outputs (ablation)

Outputs (ablation)

  • Meltwater during the spring and summer months.
  • Sublimation and evaporation can take place all year round, but mostly occur in summer.
  • Meltwater streams also transport eroded material. They are often cloudy as they contain rock flour.
  • Calving into lakes and the sea.
  • Solar energy reflected in the albedo effect.

Mass Balance

The mass balance of a glacier is influenced by inputs and outputs of glacial systems and can change over time, both long-term and short-term.

Budget

Budget

  • The mass balance (budget) is the relationship between accumulation and ablation.
    • If accumulation is greater than ablation, the glacier gains mass and the glacier snout advances.
    • If ablation is greater than accumulation, the glacier loses mass and the glacier snout retreats.
    • If accumulation is equal to ablation, the snout of the glacier remains in the same place - it is stationary.
Equilibrium lines

Equilibrium lines

  • An equilibrium line can be shown on a glacier where at any one time the amount of accumulation equals that of ablation.
    • This is also known as the firn line.
Spatial variations

Spatial variations

  • There are spatial variations in a glacial budget.
  • Most of the accumulation occurs at the upper end of a glacier because at higher altitudes it is much colder so this exceeds losses due to ablation.
    • There is, therefore, net accumulation and this part of a glacier can be called the accumulation area.
  • At the lower end of a glacier, the reverse is the case and ablation at warmer, lower altitudes exceeds accumulation.
    • So, there is net ablation and this part of a glacier is called the ablation area.

Temporal Variations and Feedback Mechanisms

The mass balance of a glacier can change over time. Feedback mechanisms also play a significant role.

Temporal variations

Temporal variations

  • There are temporal variations in a glacial budget.
  • During winter months, there is a net accumulation in the glacial budget and so the glacier expands (positive balance).
  • During summer months, there is a net ablation in the glacial budget and so the glacier reduces in size (negative balance).
Feedback mechanisms

Feedback mechanisms

  • Positive feedback - a small increase in snowfall caused by a lowering of temperature would increase the albedo of the ice surface, contributing to further cooling and more accumulation.
  • Negative feedback - higher temperatures would increase evaporation and therefore precipitation (snowfall) so more snow accumulation balances the losses from ablation at higher temperatures.
Jump to other topics
1

Tectonic Processes & Hazards

1.1

Tectonic Processes & Hazards

1.1.1Tectonic Plates1.1.2Distribution of Tectonic Hazards1.1.3Theoretical Frameworks1.1.4Earthquakes1.1.5Earthquake Hazards1.1.6Volcanoes1.1.7Tsunamis1.1.8End of Topic Test - Tectonic Processes1.1.9Exam-Style Question - Earthquakes
1.2

Natural Disasters

1.2.1Introduction to Natural Disasters1.2.2Impacts of Hazards1.2.3Comparing Hazards1.2.4Development & Governance
1.3

Natural Disaster Case Studies

1.3.1Tohoku Earthquake & Tsunami1.3.2Gorkha Earthquake1.3.3Mount Merapi Eruption
1.4

Trends & Patterns

1.4.1Disaster Trends1.4.2Prediction
1.5

Disaster Modification

1.5.1Hazard Management1.5.2Modifications1.5.3End of Topic Test - Natural Disasters1.5.4Exam-Style Question - Disaster Modification
2

Option 2A: Glaciated Landscapes & Change

2.1

Glaciated Landscapes Over Time

2.1.1Timeline of Glacial Change2.1.2Natural Causes2.1.3Ice Distributions
2.2

Periglacial Landscapes

2.2.1Periglacial Processes2.2.2Periglacial Landforms
2.3

Glacial Processes

2.3.1Mass Balance2.3.2Glacial Movement
2.4

Glacial Landforms

2.4.1Landscapes2.4.2Erosional Landforms2.4.3Erosional Landforms 22.4.4Erosional Landforms 32.4.5Depositional Landforms2.4.6Fluvioglaciation
2.5

The Future of Glaciated Landscapes

2.5.1The Value of Glaciated Landscapes2.5.2The Value of Glaciated Landscapes 22.5.3Threats to Glaciated Landscapes2.5.4Managing the Threats to Glaciated Landscapes
3

Option 2B: Coastal Landscapes & Change

3.1

Coastal Landscapes

3.1.1The Wider Coastal Landscape3.1.2Geological Structure3.1.3Lithology & Vegetation
3.2

Coastal Erosion & Deposition

3.2.1Shaping Coastlines3.2.2Coastal Formations3.2.3Sediment Transportation3.2.4Subaerial Processes
3.3

Coastal Risks

3.3.1Sea Level Change3.3.2Coastal Retreat3.3.3Coastal Flooding
3.4

Managing Coastlines

3.4.1Consequences of Coastal Recession3.4.2Engineering Management Approaches3.4.3Governance Approaches
4

Globalisation

4.1

Globalisation

4.1.1Intro to Globalisation4.1.2Development of Globalisation4.1.3Economic Policy & Globalisation4.1.4Government Policy & Globalisation4.1.5International Organisations & Globalisation4.1.6Measuring Globalisation4.1.7TNCs & Globalisation4.1.8TNCs - Aramco & Anglo-Iranian Oil
4.2

Negatives of Globalisation

4.2.1'Switched Off' Places
4.3

Global Shift

4.3.1Global Shift for Developing Nations4.3.2Global Shift for Developing Nations 24.3.3Global Shift for Developed Nations4.3.4End of Topic Test - Globalisation
4.4

Migration

4.4.1Megacities4.4.2International Migration4.4.3Country Interdependence
4.5

Culture

4.5.1Global Culture4.5.2Cultural Erosion
4.6

Measuring Development

4.6.1Measuring Development
4.7

Responses to Globalisation

4.7.1Tensions Caused by Globalisation4.7.2Government Control of Globalisation4.7.3Ethical Responses to Globalisation4.7.4End of Topic Test - Migration, Culture, & Response
5

Option 4A: Regenerating Places

5.1

Types of Economies

5.1.1Economic Activity5.1.2Employment5.1.3Economic Activity - Health & Life5.1.4Economic Activity - Education & Inequality
5.2

Function of Places

5.2.1Characteristics of Places5.2.2Changes in Places5.2.3International Influences on Places5.2.4Historic Influences on Places5.2.5The Perception of Places5.2.6Lived Experience & Attachment
5.3

Regeneration

5.3.1Migration & Capital5.3.2Success & Regeneration5.3.3Tensions & Conflict in Communities5.3.4Regeneration in the UK5.3.5Local Government Policies5.3.6Regeneration Strategies5.3.7Measuring Regeneration Success
5.4

Regeneration Case Studies

5.4.1Stratford5.4.2Salford Quays5.4.3Croyde
6

Option 4B: Diverse Places

6.1

Population Structure

6.1.1The UK6.1.2Population Characteristics6.1.3Government & Change
6.2

Past & Present Connections

6.2.1International Influence on Places6.2.2Historic Influences on Places6.2.3The Perception of Places6.2.4Image & Identity
6.3

Urban & Rural Spaces

6.3.1Perceptions of Urban Places6.3.2Perceptions of Rural Places6.3.3Evaluating Living Space
6.4

Diversity

6.4.1UK Migrations6.4.2Challenges6.4.3Tensions & Conflict6.4.4Wider Outcomes of Tensions6.4.5Managing Tensions
6.5

Urban & Rural Case Studies

6.5.1Stakeholders
6.6

Case Study - Tower Hamlets

6.6.1Background6.6.2Characteristics6.6.3Issues
6.7

Case Study - Sturton-le-Steeple

6.7.1Background6.7.2Characteristics6.7.3Issues
7

The Water Cycle & Water Insecurity (A2 only)

7.1

Hydrological Processes Global to Local

7.1.1Global Hydrological Cycle7.1.2Drainage Basin Hydrological Cycle7.1.3Water Budgets7.1.4River Regimes7.1.5Storm Hydrographs
7.2

Influences on the Water Cycle

7.2.1Causes of Drought7.2.2Impacts of Drought7.2.3Causes of Flooding7.2.4Impacts of Flooding7.2.5Climate Change & The Water Cycle7.2.6Impacts of Climate Change7.2.7End of Topic Test - The Water Cycle
7.3

Water Insecurity

7.3.1Water Stress7.3.2Causes of Water Insecurity7.3.3Water Insecurity Risk7.3.4Conflict Over Water
7.4

Water Supply Management

7.4.1Hard Engineering Schemes7.4.2Sustainable Management7.4.3Water Treaties & Framework7.4.4End of Topic Test - Water Insecurity & Management
8

The Carbon Cycle & Energy Security (A2 only)

8.1

The Carbon Cycle

8.1.1Carbon Stores8.1.2Carbon Stores 28.1.3Biological Carbon8.1.4Atmospheric Carbon8.1.5Burning Fossil Fuels
8.2

Energy Consumption

8.2.1Consumption8.2.2Access to Energy8.2.3Energy Players8.2.4Supply & Demand8.2.5Pathways8.2.6End of Topic Test - Carbon & Consumption
8.3

Alternative Energy

8.3.1Unconventional Fuels8.3.2Non-Fossil Fuels8.3.3Non-Fossil Fuels 2
8.4

Growing Demand for Resources

8.4.1Deforestation8.4.2Water8.4.3Climate Change
8.5

The Future

8.5.1Future Uncertainty8.5.2Adaptation Strategies8.5.3Mitigation Strategies
9

Superpowers (A2 only)

9.1

Superpowers

9.1.1Introduction to Superpowers9.1.2Superpowers - Economic Power & Size9.1.3Superpowers - Political & Military Power9.1.4Superpowers - Culture, Demography & Resources9.1.5Geo-Strategic Location
9.2

Hard & Soft Power

9.2.1Hard & Soft Power9.2.2Emerging Powers - China Rivalry9.2.3Emerging Powers - Chinese Sources of Power9.2.4Emerging Powers - Brazil9.2.5Emerging Powers - Russia9.2.6Emerging Powers - India9.2.7Theories of Development9.2.8Power Case Studies: Chinese One Belt One Road9.2.9Power Case Studies: Pakistan Nuclear Arms9.2.10Power Case Studies: OPEC
9.3

IGOs, TNCs & Alliances

9.3.1Superpowers & IGOs9.3.2Superpowers & TNCs9.3.3Superpowers & Global Action9.3.4Superpowers & Alliances9.3.5Superpowers & the Environment
9.4

Changing Global Influence

9.4.1Recent Tensions between Powers9.4.2China in Africa & Asia9.4.3Tensions in the Middle East9.4.4Economic Problems for Superpowers9.4.5Future Pattern of Power
10

Option 8A: Health & Human Rights (A2 only)

10.1

Human Development

10.1.1Measuring Development10.1.2Factors Improving Development10.1.3Variations in Health
10.2

Role of Governments & IGOs

10.2.1Targets & Attitudes10.2.2Financial IGOs10.2.3The United Nations (UN)10.2.4The UN's MDGs & SDGs
10.3

Human Rights

10.3.1Human Rights10.3.2Differences Between Countries10.3.3Transitions to Democracy10.3.4Differences Within Countries10.3.5The Demand for Equality
10.4

Interventions

10.4.1Geopolitical Interventions10.4.2International Intervention Players10.4.3Evaluating Geopolitical Intervention10.4.4Military Interventions10.4.5Evaluating Military Interventions
10.5

Development Aid

10.5.1Forms10.5.2Successes10.5.3Criticisms10.5.4Development Aid & the Environment10.5.5Evaluating Development Aid10.5.6Economic Inequalities
11

Option 8B: Migration & Identity (A2 only)

11.1

Globalisation & Migration

11.1.1Intro to Migration11.1.2Trends in Migration11.1.3Common Migration Patterns11.1.4Causes of Migration11.1.5Restrictions on Migration
11.2

Consequences of Migration

11.2.1Intro to Culture11.2.2Social & Demographic Tensions of Migration11.2.3Political & Economic Tensions of Migration
11.3

Nation States

11.3.1Intro to Nation States11.3.2Borders11.3.3Nationalism
11.4

Responses to Global Migration

11.4.1Responses to Global Migration11.4.2Global Organisations11.4.3IGOs and World Trade11.4.4Financial IGOs11.4.5Environmental IGOs
11.5

Sovereignty & Identity

11.5.1Sovereignty & Nationalism11.5.2Complex Identities11.5.3Challenges to National Identities11.5.4Tensions within Nations11.5.5Failed States

Practice questions on Mass Balance

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    What is another word for the outputs of a glacial system?Multiple choice
  2. 2
    How much solar radiation is reflected in the albedo effect?Multiple choice
  3. 3
    If accumulation is equal to ablation in the mass balance of a glacier, what happens?Multiple choice
  4. 4
    Which of the following are true of mass balances in glaciers?True / false
  5. 5
    During which season is there a net ablation in the glacial budget?Multiple choice
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Periglacial Landforms

Glacial Movement