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The Ayles Ice Shelf was one of six major ice shelves in Canada, all on the north coast of Ellesmere Island, Nunavut. The ice shelf broke off from the coast on August 13, 2005, forming a giant ice island thick and measuring around by in size (approximately 66 km² or ² in area or 2.6 km³ in volume). The oldest ice in the ice shelf is believed to be over 3,000 years old. The ice shelf was at (), approximately south of the North Pole. The Ayles Ice Shelf, like the nearby Mount Ayles, was named for the Arctic explorer Adam Ayles, who served under George Nares as the Petty Officer of HMS ''Alert'' in the British Arctic Expedition.〔(Wairarapa Times-Age newspaper article biography of Adam Ayles )〕 A 1986 survey of Canadian ice shelves found that 48 square km (3.3 cubic km) of ice calved from the Milne and Ayles ice shelves between 1959 and 1974.〔Jeffries, Martin O. ( Ice Island Calvings and Ice Shelf Changes, Milne Ice Shelf and Ayles Ice Shelf, Ellesmere Island, N.W.T. ). ''Arctic'' 39 (1) (March 1986).〕 == Ayles Ice Island == On August 13, 2005, the entire shelf broke clear from the coast of Ellesmere, forming a new ice island. It is believed to be the largest shelf breakup of its kind in Canada in over 30 years.〔(Giant ice island breaks off Arctic shelf ), Guardian Unlimited〕 The event was registered on seismometers in northern Canada, and it was also verified via satellite imagery. The breakup was noticed by the Canadian Ice Service at the time that it occurred, but it took a further 16 months to fully reconstruct the breakup sequence from past satellite images captured by MODIS, to determine the climatic conditions during the event, and for the event to garner public attention. The event, which some have linked to global warming, is similar to the 2002 breakup of the Larsen B Ice Shelf in Antarctica. The speed of the breakup is also remarkable; it took less than an hour. Canada has lost approximately 90% of its ice shelves in the last hundred years.〔(Arctic Ice Shelf Broke Off Canadian Island ), New York Times〕 Within days of the breakup, the former shelf had drifted over from Ellesmere Island before freezing into the sea ice for the winter. It was estimated in May, 2007 to be between and thick, on average. The freed segment of the ice shelf, known as Ayles Ice Island, drifted southwesterly for two years, and in January 2007 accelerated into the open Arctic Ocean, causing concern for oil rig operators in the Beaufort Sea north of Prudhoe Bay. In August 2007, however, the island became wedged into the Sverdrup Inlet of the Queen Elizabeth Islands. Although scientists initially thought it was likely to remain there for some time, possibly permanently, it soon afterwards broke into two parts and resumed movement.〔 There is concern that the ice islands may become a hazard for ships and oil platforms.〔(Arctic ice shelf collapse poses risk: expert ), CBC news 〕 While the formation of the Ayles Ice Island received widespread attention at the time due to the availability of satellite imagery and the ability of news media and scientists to visit the island, it was by no means unprecedented. On August 14, 1946, a U.S. Air Force patrol plane flying north of Port Barrow, Alaska spotted an ice island, dubbed T-1, which was wide and across. It was estimated to be from 240 to thick, with sides that rose from 30 to above the sea surface - much larger than the Ayles Ice Island. Over the following three years, it travelled around along the Beaufort Eddy, a slow-moving ocean current that flows eastward across the North Pole, then back west along the coast. In 1950, the U.S. Air Force 58th Reconnaissance Squadron was ordered to find T-1, and any other ice islands in the Arctic. In July, 1950, T-2 was found, a roughly rectangular ice island estimated to be by by dimension. In 1947, a joint U.S.-Canadian expedition had noted and photographed a fresh water sea formation in the sea off Ellesmere Island. From a photographic examination of its ridges, T-2 was discovered to be the same ice island spotted off Ellesmere Island in 1947. Later in July 1950, the U.S. Air Force found T-3, a kidney-shaped island, nine by four and a half miles. This was later occupied for brief periods in the early and mid-1950s. In August 1951, T-1 was relocated, nestled along the coast of Ellesmere Island. It is not known how long prior T-1, T-2, and T-3 had been formed, but it is believed they had calved from ice shelves on northern Ellesmere Island.〔"The Mysterious Floating Islands of the Arctic", Reader's Digest January 1952〕 There are an estimated 80 ice islands in Canada's High Arctic, most of them part of the pack ice that covers the region. Between August 1961 and April 1962, almost 600 square kilometres of ice broke away from the Ward Hunt Ice Shelf. 〔G. Hattersley-Smith, 1963 "The Ward Hunt Ice Shelf: recent changes of the ice front" Journal of Glaciology 4:415-424. 〕 This event was attributed to tidal and seismic events. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ayles Ice Shelf」の詳細全文を読む スポンサード リンク
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