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 is a large, persistent body of land-based ice that forms over many years where the 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 of snow is greater than its loss (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). The ice in a glacier flows very slowly downhill, wearing away the rock underneath. Antarctica has the greatest area of glaciers but there are also many glaciers in parts of the Arctic such as Greenland, Canada, the Russian Definitions of the Arctic vary according to environmental, geographical, political, cultural and scientific perspectives. Some scientists define the Arctic as areas having a high latitude, long winters, short, cool summers,... More islands, Alaska, Iceland and Svalbard. Arctic glaciers are very sensitive to changes in summer temperatures, and are used to monitor climatic changes.