Glacier Mass Balance with Upward ELA Explained

The Equilibrium Line Altitude (ELA) is the elevation where a glacier's annual gain (accumulation) equals its annual loss (ablation).

Understanding Upward ELA Movement

• When the ELA moves upwards, it indicates that the zone of net melting (ablation) is extending to higher altitudes, or the zone of net snowfall (accumulation) is shrinking.
• This signifies that, overall, ablation is exceeding accumulation.

Glacier Mass Balance Definition

Glacier mass balance is the difference between the total mass gained (accumulation) and the total mass lost (ablation) over a specific period. It can be represented as:

$Mass Balance = Accumulation - Ablation$

Connecting ELA Movement and Mass Balance

• An upward moving ELA directly implies that $Accumulation < Ablation$.
• Therefore, the calculation $Accumulation - Ablation$ results in a negative value.
• This means the glacier is losing mass overall.

Conclusion: A glacier with an upward moving equilibrium line altitude has a negative mass balance.