Glacier Mass Balance

The net balance between the accumulation of new snow and ice on a glacier's upper reaches and the ablation, through melting, sublimation and calving, that removes ice lower down, which together determine whether a glacier as a whole is gaining or losing mass over a given year. A glacier with a sustained negative mass balance thins and retreats even if its front continues to flow forward, and monitoring mass balance across the world's glaciers is a principal method for tracking the pace of ice loss under a warming climate.