Cryospheric processes and sea-level change

Overview

Accumulation in a glacier system, mass balance of a glacier and negative mass balance.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Define accumulation in a glacier system.

   Model answer

   Accumulation is the addition of mass to a glacier, mainly as snowfall but also from avalanches, blown snow and freezing rain.

2. 2

   Define ablation.

   Model answer

   Ablation is the loss of mass from a glacier by melting, sublimation, calving and the removal of snow by wind.

3. 3

   What is the mass balance of a glacier?

   Model answer

   The difference over a year between the mass it gains by accumulation and the mass it loses by ablation, which decides whether it grows, shrinks or holds steady.

4. 4

   What does a negative mass balance mean for the snout of a glacier?

   Model answer

   Losses exceed gains, so the glacier retreats and its snout moves back up the valley.

5. 5

   Where on a glacier is the equilibrium line found?

   Model answer

   At the altitude where a year of accumulation exactly equals a year of ablation, separating the accumulation zone above from the ablation zone below.

6. 6

   Explain how calving removes mass from an ice sheet.

   Model answer

   Where ice reaches the sea it floats and fractures, and blocks break away as icebergs that drift off and melt in the ocean.

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