Ice shelf

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The largest ice shelves in Antarctica (as of 2007):
  • Ross (472,960 km²)
  • Filchner-Ronne (422,420 km²)
  • Amery (62,620 km²)
  • Larsen C (48,600 km²)
  • Riiser-Larsen (48,180 km²)
  • Fimbul (41,060 km²)
  • Shackleton (33,820 km²)
  • George VI (23,880 km²)
  • West (16,370 km²)
  • Wilkins (13,680 km²)
  • When ice shelves or ice shelf refers to a large sheet of ice formed on the sea swims and glaciers , rivers of ice or ice caps is fed and is still connected to it. One speaks of an ice shelf when the plate rises at least two meters above sea level, usually between 200 and 1000 meters thick. It is characteristic of ice shelves that icebergs break off again and again at the very edge . This process is known as calving .

    Description and characteristics

    Ice shelf edge

    When the ice from glaciers or ice streams reaches the coast, it floats on the sea from a certain water depth. The point from which the ice masses no longer stand on the seabed, but rather begin to float, is called the grounding line . Where the ice shelf in the water pushes itself over rocky shallows, hills or folds appear in the ice. Such ice domes counteract the movement of the pushing ice, so that tensions arise. Otherwise, the ice shelf is flat and level, which is why the calving creates so-called table icebergs . This is the typical shape of the icebergs in Antarctica.

    The stability and the mass balance of the ice shelf are important for the rise in sea level . On the one hand, the melting of floating (freshwater) ice slightly increases the sea level, on the other hand, the plastic ice of the inland glaciers flows faster into the sea when ice shelves break away from the mainland. It is currently unclear whether the retreat of the ice shelf edge has been a normal process since 1957 or whether it is already an effect of global warming.

    The largest ice shelf areas are in the Antarctic :

    In the West Antarctic and the Antarctic Peninsula , increased cracking and melting of the ice shelf tables has been observed since 1995, which is at least partly due to the local temperature rise in connection with global warming .

    The Larsen A Ice Shelf dissolved in 1995, followed by the Larsen B Ice Shelf in 2002 . In 2008 and 2009, parts of the Wilkins Ice Shelf broke open , which previously provided the connection to Charcot Island .

    Current recordings of the Wilkins Ice Shelf can be found on the 'Webcam' from Space offered by ESA .

    Schematic representation of glaciological and oceanographic processes on the Antarctic coast: Over the Antarctic ice sheet, precipitation falls in the form of snow (precipitation). The ice sheet is largely frozen to the ground (back stress) and has built up to a thickness of over 4000 m. The ice flows from the continent on all sides, e.g. T. concentrated in ice streams. On the coast, the ice loses contact with the ground in the area of ​​the grounding line, becomes significantly thinner (a few 100 m) and forms an ice shelf above the shelf (Continental shelf), which is still connected to the ice sheet , but already swims. If the ice shelf flows over a shoal, ice dome (ice rises) are formed. At the edge of the ice shelf, tabular icebergs break off (Calving line, Iceberg calving) and melt in warmer water on their way around the Antarctic. A coastal polynya occurs when cold offshore winds (catabatic winds) drive the sea ice away from the coast. In connection with the formation of new ice, cold, salty and therefore heavy water is created, which flows down the continental slope and represents the essential mechanism for the formation of the oceanic bottom water in the deep sea.

    Web links

    Commons : Ice Shelf  - Album with pictures, videos and audio files

    Individual evidence

    1. Noerdlinger, Peter D .; Brower, Kay R. (2007): The melting of floating ice raises the ocean level , in: Geophysical Journal International, Vol. 170, July 2007, pp. 145-150, online .
    2. Antarctica: gigantic ice surface is falling apart. DER SPIEGEL , March 19, 2002, accessed December 4, 2009 .
    3. Alexander Stirn : Collapsing Ice Shelf: Antarctic glaciers run out. DER SPIEGEL , March 8, 2003, accessed December 4, 2009 .
    4. Antarctica: Warming caused ice shelf breakage. DER SPIEGEL , September 12, 2014, accessed January 3, 2014 .
    5. Antarctic Ice: Large cracks discovered in Wilkins' shield. DER SPIEGEL , December 1, 2008, accessed December 4, 2009 .
    6. ^ Wilkins pack ice: Ice bridge breaks in Antarctica. DER SPIEGEL , April 5, 2009, accessed December 4, 2009 .