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The Larsen Ice Shelf is a long, fringing ice shelf in the northwest part of the Weddell Sea, extending along the east coast of Antarctic Peninsula from Cape Longing to the area just southward of Hearst Island. Named for Captain Carl Anton Larsen, the master of the Norwegian whaling vessel ''Jason'', who sailed along the ice front as far as 68°10' South during December 1893. In finer detail, the Larsen Ice Shelf is a series of three shelves that occupy (or occupied) distinct embayments along the coast. From north to south, the three segments are called Larsen A (the smallest), Larsen B, and Larsen C (the largest) by researchers who work in the area.〔 File:Larsen iceshelves.png|Larsen A and Larsen B iceshelves marked in red. File:Glacier-ice shelf interactions.svg|Glacier-ice shelf interactions. File:Antarctic Peninsula, the Larsen Ice Shelf, and the sea ice covered waters around the region.jpg|Clear view of the Antarctic Peninsula, the Larsen Ice Shelf, and the sea ice covered waters around the region. ==Ice shelf== The collapse of Larsen B has revealed a thriving chemotrophic ecosystem 800 m (half a mile) below the sea. "Despite near freezing and sunless conditions, a community of clams and microbial mats are flourishing in undersea sediments. () The discovery was accidental. U.S. Antarctic Program scientists were in the northwestern Weddell Sea investigating the sediment record in a deep glacial trough twice the size of Texas. Methane and hydrogen sulfide associated with cold seeps is suspected as the source of the chemical energy powering the ecosystem. The area had been protected by the overlying ice sheet from debris and sediment which was seen to be building up on the white microbial mats after the breakup of the ice sheet. The clams were observed clustered about the vents. Studies show that in the middle of the present interglacial the former Larsen A region, which was the furthest north and outside the Antarctic Circle, had previously broken up and reformed only about 4,000 years ago, although the former Larsen B had been stable for at least 10,000 years.〔 The maximal ice age on the current shelf dates from only two hundred years ago. The speed of Crane Glacier increased threefold after the collapse of the Larsen B and this is likely to be due to the removal of a buttressing effect of the ice shelf. Data collected in 2007 by an international team of investigators through satellite-based radar measurements suggests that the overall ice-sheet mass balance in Antarctica is increasingly negative.〔Perlman, David (2008) "Antarctic Glaciers Melting More Quickly" San Francisco Chronicle (January 26) p. A2, (online )〕 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「Larsen Ice Shelf」の詳細全文を読む スポンサード リンク
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