The frozen part of the Earth's surface. The cryosphere includes the polar ice caps, continental ice sheets, mountain glaciers, sea ice, snow cover, lake and river ice, and permafrost.
In the next 100 years between one third and one half of the world's mountain glaciers could melt, affecting the water supply to rivers and thus hydroelectric dams and agriculture. As is already being observed in Alaska, the areal extent and depth of permafrost are projected to decline, resulting in adverse effects on human infrastructure. A decrease in the extent and thickness of sea-ice will likely improve the navigability of the Arctic Ocean.
including the ice sheets of Greenland and Antarctica, continental glaciers and snow fields, sea ice and permafrost, derives its importance to the climate system from its high reflectivity (albedo) for solar radiation, its low thermal conductivity, its large thermal inertia and, especially, its crucial role in driving deep ocean water circulation. Because the ice sheets store a large amount of water, variations in their volume are a potential source of sea-level variations.( IPCC)