An ice body that covers an area of continental size, generally defined as covering 50 000 km2 or more.
Currently there are only two ice sheets, the Greenland Ice Sheet and the Antarctic Ice Sheet. The latter is sometimes subdivided into the East Antarctic Ice Sheet and the West Antarctic Ice Sheet. See ice cap
Glossary of glacier mass balance and related terms. Working Group on Mass-balance Terminology and Methods of the International Association of Cryospheric Sciences (IACS)
Elements of the Greenland ice sheet hydrologic system. (a) In the accumulation zone above the equilibrium line altitude (ELA), water percolating through the snow/firn can pool into slush regions and channelize into supraglacial streams. In the ablation zone beneath the ELA, meltwater pools in supraglacial lakes and flows through streams into crevasses and moulins, entering englacial and subglacial conduits emerging into proglacial rivers and lakes. As meltwater moves through the system, erosional debris increases sediment concentration making glacial-melt lakes and rivers sediment-rich (leaving precipitation and snowmelt lakes clear of sediment). Finally, meltwater entering the ocean produces a buoyant sediment plume in the fjord. (b) Differences for marine-terminating glaciers lie in meltwater outlet mechanisms. Sediment-rich subglacial discharge released tens to hundreds of meters below the water surface either rises to form a buoyant plume or forms a turbidity current beneath the surface. Source : Modified from Cuffey and Paterson (2010)
https://www.researchgate.net/figure/Elements-of-the-Greenland-ice-sheet-hydrologic-system-a-In-the-accumulation-zone-above_fig1_265050040?_sg=LS3GOFKRlYjSsNWZC3yNZU2wMCfoBW079CrTgMclb6lU7jdKZaU03-hXOsEyNQ3H3pP8nTyY9IH_lhkKpEomBg