Ice shelves of Antarctica

Ice shelves of Antarctica. These vast, floating platforms of glacial ice are permanent extensions of the Antarctic ice sheet, fringing much of the continent's coastline. They form where ice flows from the grounded ice sheet onto the ocean, remaining attached to the landmass. These critical features regulate ice flow from the interior and play a key role in global sea level and ocean circulation.

Formation and characteristics

Ice shelves form through the accumulation and compaction of snow over millennia, which transforms into glacial ice that flows outward under its own weight. This ice, fed by major outlet glaciers and ice streams, moves seaward until it begins to float upon reaching the grounding line in the Southern Ocean. The largest shelves are found in the Weddell Sea, Ross Sea, and along the coast of West Antarctica. They are characterized by their immense thickness, often hundreds of meters, and their relatively flat, tabular surfaces, which can calve off to form massive tabular icebergs. The interaction between the ice shelf's base and the relatively warm Circumpolar Deep Water is a critical factor in their stability.

Major ice shelves

The Ross Ice Shelf is the largest, covering an area roughly the size of France, and is fed by ice from the Transantarctic Mountains and the West Antarctic Ice Sheet. The Ronne-Filchner Ice Shelf in the Weddell Sea is the second largest, a complex system influenced by ice from the Antarctic Peninsula and East Antarctica. Other significant shelves include the Amery Ice Shelf in East Antarctica, a key drainage basin for the Lambert Glacier, and the Larsen Ice Shelf, which once extended along the eastern coast of the Antarctic Peninsula. Smaller but important shelves include the George VI Ice Shelf and the Shackleton Ice Shelf.

Stability and disintegration

The stability of Antarctic ice shelves is threatened primarily by basal melt from warming ocean currents and surface melt from increasing air temperatures. The dramatic collapse of sections of the Larsen Ice Shelf, notably Larsen A in 1995 and the much larger Larsen B in 2002, provided stark evidence of rapid disintegration linked to climate change. Similar processes are observed at the Thwaites Glacier and Pine Island Glacier in West Antarctica, where weakening ice shelves accelerate the flow of inland ice. The presence of meltwater ponds, crevasses, and rifts can further destabilize shelves through processes like hydrofracture.

Role in sea level rise

Ice shelves themselves contribute directly to sea level rise only when they melt, as they are already displacing ocean water. Their crucial role is as a buttress; they provide back pressure that slows the seaward flow of grounded ice sheet ice. When an ice shelf thins, breaks apart, or collapses entirely, this buttressing effect is reduced or lost, allowing glaciers to accelerate. This dynamic discharge of land ice into the ocean is a primary mechanism for potential rapid sea level rise. Research on the Thwaites Glacier, often termed the "Doomsday Glacier," highlights how shelf disintegration could unlock vast volumes of ice from the West Antarctic Ice Sheet.

Research and monitoring

International scientific programs like the British Antarctic Survey, NASA, and the Alfred Wegener Institute conduct extensive research on ice shelves. Monitoring utilizes satellite missions such as ICESat, CryoSat-2, and the Copernicus Programme's Sentinel-1 radar satellites to measure thickness, flow velocity, and grounding line retreat. Field campaigns, including drilling projects by the Antarctic Drilling Project and the use of autonomous underwater vehicles like Boaty McBoatface, gather data on ocean conditions and basal melt. This research is coordinated through bodies like the Scientific Committee on Antarctic Research to improve projections for the Intergovernmental Panel on Climate Change.

Category:Antarctic ice shelves Category:Geography of Antarctica