The Glacial Budget

The Glacial Budget

1. The difference between accumulation (snowfall) and ablation (snowmelt). A negative budget has more ablation than accumulation, and the glacier retreats

2. Zone of accumulation

   • Most of accumulation occurs higher up the glacier where it stays colder
     • Snow is added each winter

3. Zone of ablation

   • Most ablation happens down the valley, towards the snout of the glacier where it gets warmer
     • The ice surface melts in spring and summer and ice is lost by evaporation

4. A positive glacial budget sees the glacier advance down the valley

5. A negative budget means the glacier retreats up the valley

6. Glacial Retreat

   • Warming temperatures are causing glacial retreat
   • Evidence of Glacial retreat
     • Increases in lakes and rivers fed my meltwater
     • Debris left by the glacier as it retreats
     • Old maps marking former glacier extent
     • Recent arial photos and satellite images
     • Old paintings and photos showing where a glacier used to extend to
     • Old measurements made by geographers in the past
     • Data from glacier measuring devices

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