2.A4 Mass balance and the importance in understanding glacial dynamics and the operation of glaciers as systems

Question 1

Glacial mass balance definition -

Answer 1

Mass balance is defined as the gains and losses of the ice store in the glacial system of accumulation and ablation.

Question 2

Accumulation -

Answer 2

Results from direct snowfall and other precipitation this may include meltwater.

Question 3

Ablation -

Answer 3

The snow and ice are travelled down the valley by glacier movement until they reach lower areas where they are lost to the system by melting, evaporation or sublimation. This is known as ablation. Refers to the glacial output

Question 4

Accumulation zone -

Answer 4

Towards the upper part of the glacier

Question 5

Ablation zone -

Answer 5

Towards the lower parts of the glacier.

Question 6

Equilibrium zone -

Answer 6

Is known as the losses of the ablation are balanced with the gains of accumulation.

Question 7

Temporal variations in the mass balance of ablation and accumulation -

Answer 7

During winter months - there is net accumulation in the glacial budget and so the so the glacier expands experiencing positive balance, whereas the summer the net ablation in the glacial budget and so reduces in size experiencing a negative mass balance.

Question 8

Positive feedback -

Answer 8

Conditions get worse, where ablation exceeds accumulation. Therefore advances.

Question 9

Negative feedback -

Answer 9

When accumulation exceeds ablation therefore resulting in a positive mass balance allowing the glacier to gain net mass. This allows a glacier to retreat.

Question 10

The Greenland Ice Sheet Case study on how the ice sheet is effected by mass balance -

Answer 10

One of the worlds two remaining ice sheets. Due to recent climate change a number of changes are occurring to the mass balance and this shows a -30 mass balance. Research has shown that Greenland ice sheet has a negative mass balance, evidence of the positive feedback on the Greenland Ice sheet can be suggested through anthropogenic causes and cause the ice sheet to melt rapidly. Albedo is reduced over time to the reduction of snow ice therefore increases the temperature of the land, this may lead to a high quantity of methane released from the glacier and would also have huge impacts on the rising sea levels potentially 6m higher.

Question 11

Reasoning for variations of accumulation and ablation -

Answer 11

A glacier has positive and negative feedback systems to keep it in dynamic equilibrium.

Question 12

Reasons for fluctuations in accumulation -

Answer 12

• Increased input of snowfall leading to longer mass overtime.
• Lower temperatures - less melting.
• Lower wind speeds -slows rates of transfer out systems.
• Albedo increased as the surfaces do not absorb as not as much is absorbed whereas less albedo would result in more ablation and melting from higher outputs.
  Lower rates of insolation (income of solar energy)

Question 13

Reasons for fluctuations in ablation -

Answer 13

Opposite of accumulation factors (the literal opposite) -
Lower rates of input - less snowfall reduces future ice formation
Increase in global temperatures - reduces snow formation, and increases rate of melting
Higher wind speeds - transfer out of the system increases and prevents snow from settling
Increased insolation - lowered albedo effect