West Antarctic Ice Sheet

The West Antarctic Ice Sheet is the portion of Antarctica’s ice sheet west of the Transantarctic Mountains. Much of it rests on bedrock below sea level, making it vulnerable to ocean-driven retreat.

Marine ice sheet instability: A feedback in which retreat of a marine ice-sheet grounding line onto deeper bedrock can promote further retreat. Much of the ice sheet rests below sea level, creating conditions for this retreat feedback.
Thwaites Glacier: A large, fast-moving glacier in West Antarctica that drains into the Amundsen Sea. Its retreat and ice-shelf changes are central examples of contemporary West Antarctic ice loss.
Sea-level rise: A long-term increase in the average level of the global ocean. Loss of grounded West Antarctic ice adds water to the ocean and raises global sea level.
Transantarctic Mountains: A mountain range crossing Antarctica and separating East Antarctica from West Antarctica. The range marks the geographic division used to distinguish the West Antarctic Ice Sheet.
Ice-sheet tipping point: A threshold beyond which an ice sheet may undergo self-sustaining change toward a substantially different state. Researchers debate whether parts of West Antarctica have crossed or may cross such thresholds.
Grounding line: The boundary where grounded glacier ice begins to float as an ice shelf. Its movement marks the inland limit of floating ice and tracks retreat in West Antarctica.
Pine Island Glacier: A major West Antarctic glacier flowing into Pine Island Bay in the Amundsen Sea. Its thinning and retreat illustrate ocean-driven change in the region.
Antarctic Ice Sheet: The vast body of land-based ice covering most of Antarctica, comprising the East and West Antarctic ice sheets. West Antarctica is one of two principal regions contributing to Antarctic ice-sheet change.
Bedrock topography: The shape and elevation of the solid ground beneath an ice sheet. Sub-sea-level basins beneath West Antarctica influence grounding-line stability.
Antarctic ice-sheet modeling: The numerical simulation of Antarctic ice-sheet dynamics and their interactions with climate and oceans. Models estimate future West Antarctic retreat, but projections depend on uncertain processes and inputs.

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