Total glacier mass balance

Graphs showing the hypsometry of two neighbouring glaciers in Svalbard. Lovenbreen has more area at higher elevations and would therefore have a more positive mass balance. Glacier mass balance data from the World Glacier Monitoring Service

If we want to know whether the glacier as a whole is gaining or losing mass, we need to add up the net mass balance for each part of the glacier, as it is losing mass in some areas while gaining mass elsewhere. To do this, we need to know about the shape of the glacier, specifically, how much area it has at each elevation. This concept is known as hypsometry.

If a glacier has a lot of its area at high elevations, it has a top-heavy hypsometry, and vice versa. Two neighbouring glaciers can experience the same snowfall and the same melting at each elevation but have very different total mass balances due to differences in their hypsometry.