Marine ice-sheet instability

Marine ice-sheet instability is a feedback in which retreat of grounded ice across a bed that deepens inland can accelerate because the grounding line moves into progressively thicker ice.

Grounding line: The boundary where a grounded glacier or ice sheet begins to float as an ice shelf. Its inland migration is the central moving boundary in the instability.
Ice sheet: A continent-scale mass of glacial ice covering land and flowing outward under its own weight. Marine ice-sheet instability is a possible retreat behavior of this broader ice mass.
West Antarctic Ice Sheet: The Antarctic ice-sheet sector west of the Transantarctic Mountains, much of it grounded below sea level. Its marine setting and inland-deepening basins make it a major potential site of instability.
Marine ice-cliff instability: A proposed feedback in which tall, unsupported ice cliffs fail under their own stress, accelerating ice loss. It concerns cliff failure, rather than grounding-line migration over a retrograde bed.
Ice-sheet grounding-line dynamics: The flow and migration of the boundary between grounded ice and floating ice. These dynamics describe how ice flow responds as the grounding line retreats.
Ice shelf: A floating extension of a glacier or ice sheet that remains attached to land ice. Its contact with grounded ice helps set flow across the grounding line.
Thwaites Glacier: A large West Antarctic glacier that drains into the Amundsen Sea. Its retreat and exposure of deep inland basins are closely studied in relation to the instability.
Marine ice-sheet stabilization: Processes that slow or halt retreat of grounded ice connected to the ocean. Bed and ice-shelf effects can counter the runaway tendency associated with instability.
Retrograde slope: A bed slope that deepens in the inland direction beneath a glacier or ice sheet. Retreat onto this geometry can place the grounding line beneath thicker ice.
Marine ice sheet: An ice sheet grounded on bedrock that lies below sea level and is connected to the ocean. This is the type of ice sheet that can undergo the instability.

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