Mass Balance
Glacier growth and decrease depends on the balance between accumulation and ablation. At low temperatures only a small amount of snowfall is needed to support a glacier, while in warmer environments a higher seasonal supply is necessary. The difference between the accumulated snow and ice and the ablation, is known as the glacier’s mass balance. If more mass has accumulated than melted, the mass balance is positive, i.e. , the glacier is growing. If more has melted than what has accumulated, the mass balance is negative, i.e. the glacier is shrinking.