Furthermore, the mass breakout of icebergs from Larsen Ice Shelf between 19, though generally ascribed to global warming, is thought to have occurred because summer meltwater on the surface of the shelf filled nearby crevasses.
In addition, on a number of occasions, iceberg calving has been observed immediately after the collision of another iceberg with the ice front. The swell causes the tongue to oscillate until it fractures. This bending stress is enhanced in the case of glacier tongues (long narrow floating ice shelves produced by fast-flowing glaciers that protrude far into the ocean). With the use of tiltmeters (tools that can detect a change in the angle of the slope of an object), scientists monitoring iceberg-calving events have been able to link the breaking stress occurring near the ice front to long storm-generated swells originating tens of thousands of kilometres away. Iceberg calving may be caused by ocean wave action, contact with other icebergs, or the behaviour of melting water on the upper surface of the berg. Larsen Ice Shelf Encyclopædia Britannica, Inc. Some minor ice shelves generate large iceberg volumes because of their rapid velocity the small Amery Ice Shelf, for instance, produces 31 cubic km (about 7 cubic miles) of icebergs per year as it drains about 12 percent of the east Antarctic Ice Sheet. Since the shelf normally possesses cracks and crevasses, it will eventually fracture to yield freely floating icebergs. The exposed seaward front of the ice shelf experiences stresses from subshelf currents, tides, and ocean swell in the summer and moving pack ice during the winter. Under the pressure of the ice flowing outward from the centre of the continent, the ice in these shelves moves seaward at 0.3–2.6 km (0.2–1.6 miles) per year. Floating ice shelves fringe about 30 percent of Antarctica’s coastline, and the transition area where floating ice meets ice that sits directly on bedrock is known as the grounding line. Floating ice shelves are a continuation of the flowing mass of ice that makes up the continental ice sheet.
The mass of a tabular iceberg is typically several billion tons. A typical newly calved iceberg of this type has a diameter that ranges from several kilometres to tens of kilometres, a thickness of 200–400 metres (660–1,320 feet), and a freeboard, or the height of the “berg” above the waterline, of 30–50 metres (100–160 feet). Icebergs of the Antarctic calve from floating ice shelves and are a magnificent sight, forming huge, flat “tabular” structures.
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