Mass Balance

October 14, 2020

Mass balance

Photographer: Andrea Rapposelli
Summary Authors: Andrea Rapposelli

Essential for a glacier to survive is its mass balance - the difference between accumulation and ablation (melting or sublimation). Climate change can cause large variations in temperature ranges, both in their averages and in snowfall precipitation as well as changes in the mass balance. A glacier with a negative balance is not in equilibrium and will tend to retreat. A glacier with a positive balance is also in a state of imbalance but will advance to restore it. The retreat of the glacier manifests itself in the loss of its lower region which because it’s at a lower altitude is normally warmer than the higher zones. Glacier melting reduces overall ablation, thus increasing mass balance and potentially restoring equilibrium. If the mass balance of a significant part of the glacier accumulation zone is negative, it's out of balance with the climate and will tend to melt if a colder climate and/or an increase in solid precipitation does not occur. The photograph above of the Montabel glacier was taken near the town of Breuil-Cervinia. The central rocky tip was covered by snow a few decades ago. Photo taken July 22, 2020.

Photo Details: Camera PENTAX K-5; telephoto lens 18-55 mm at 55mm; Software Adobe Photoshop CC 2015 (Windows); Exposure Time 0.010s (1/100); Aperture ƒ/9.0; ISO equivalent 400; Focal Length (35mm) 82.