Editing Cryosphere Dynamics (section)

== The Physics of Land Ice: Ice Sheets and Glaciers ==

Land ice forms when snow accumulates over many years, compresses under its own weight, and eventually recrystallizes into dense, solid glacier ice. The vast majority of the world's land ice is locked in the two major continental '''ice sheets''': the Antarctic Ice Sheet and the Greenland Ice Sheet.

=== Mass Balance and Flow ===
The physical health of a glacier or ice sheet is determined by its '''mass balance'''—the net difference between accumulation (gaining mass, primarily through snowfall) and ablation (losing mass through melting, sublimation, and iceberg calving). 

While ice appears solid, under immense pressure, it exhibits a property known as plastic deformation; it flows downhill like a highly viscous fluid. The speed of this flow is governed by internal deformation and '''basal sliding'''. When meltwater reaches the base of a glacier, it acts as a lubricant between the ice and the underlying bedrock, significantly accelerating the flow of ice toward the ocean.

=== Ice Shelves and Marine-Terminating Glaciers ===
In Antarctica and Greenland, massive rivers of ice flow outward from the interior and meet the ocean, forming '''ice shelves'''—thick slabs of ice that float on the sea surface but remain attached to the grounded land ice behind them. These floating shelves act like massive buttresses or physical corks, holding back the flow of the land ice. If warm ocean water erodes an ice shelf from below, causing it to collapse, the grounded glaciers behind it often rapidly accelerate their flow into the ocean.