Encompasses all the ways in which a body of ice (a A glacier is a large, persistent body of land-based ice that forms over many years where the accumulation of snow is greater than its loss (ablation). The ice in a... More or A mass of glacial land ice extending more than 50,000 square kilometers (20,000 square miles). The two ice sheets on Earth today cover most of Greenland and Antarctica and together... More) gains mass at its surface, such as snowfall and rime formation. However, it excludes ice gained from ice flow. The opposite of Encompasses all the ways in which a body of ice (a glacier or ice sheet) gains mass at its surface, such as snowfall and rime formation. However, it excludes ice... More is Encompasses all the ways in which ice mass is lost from the surface of a glacier or ice sheet, such as melting at the surface or the base (underside), and evaporation. However, ablation... More. Rates of ablation and accumulation affect the The difference between the amount of ice a glacier gains in winter and the amount lost in summer. A glacier which is gaining mass has a positive mass balance: more ice is... More of a glacier.