Antarctic sea ice

Antarctic sea ice is seawater frozen at the ocean surface around Antarctica. It expands during the austral winter and retreats during the summer.

Sea ice formation: The freezing of ocean water into floating ice as heat is removed from the surface. Cooling surface water creates the seasonal ice cover around Antarctica.
Brine rejection: The expulsion of concentrated saltwater from ice as seawater freezes. Salt expelled during freezing increases the density of water beneath new ice.
Sea ice concentration: The fraction of a specified ocean area covered by sea ice. Satellite concentration maps are used to estimate Antarctic sea-ice extent.
Antarctic bottom water: A cold, dense water mass formed near Antarctica that spreads along the ocean floor. Salt released during sea-ice formation helps create dense shelf waters that feed this mass.
Antarctic sea-ice variability: Changes in Antarctic sea-ice coverage across seasons, years, and longer periods. Large natural swings complicate interpretation of long-term trends.
Sea ice drift: The movement of floating sea ice under winds, currents, and interactions with other ice. Drift redistributes Antarctic ice and helps determine its extent and shape.
Sea ice thickness: The vertical distance from the top surface of sea ice to its underside. Thickness complements mapped extent when measuring the Antarctic ice cover.
Sea ice extent: The area of ocean with sea-ice concentration above a specified threshold. This standard measure tracks the seasonal reach of Antarctic sea ice.
Antarctic ice shelves: Floating extensions of Antarctic glaciers and ice streams that border much of the continent. Sea ice can reduce ocean-wave exposure and affect conditions near ice-shelf fronts.
Antarctic sea-ice minimum of 2023: The record-low austral-summer Antarctic sea-ice extent observed in 2023 in the satellite era. Its unprecedented low extent intensified questions about the causes of recent losses.

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