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Dye 3 is an ice core site and previously part of the Distant Early Warning (DEW) line, located at (, 2480 masl)〔(【引用サイトリンク】title=The Distant Early Warning (DEW) Line: A Bibliography and Documentary Resource List )〕 in Greenland. As a DEW line base, it was disbanded in years 1990/1991.〔 An ice core is a core sample from the accumulation of snow and ice that has re-crystallized and trapped air bubbles over many years. The composition of these ice cores, especially the presence of hydrogen and oxygen isotopes, provides a picture of the climate at the time. Ice cores contain an abundance of climate information. Inclusions in the snow, such as wind-blown dust, ash, bubbles of atmospheric gas and radioactive substances, remain in the ice. The variety of climatic proxies is greater than in any other natural recorder of climate, such as tree rings or sediment layers. These include (proxies for) temperature, ocean volume, precipitation, chemistry and gas composition of the lower atmosphere, volcanic eruptions, solar variability, sea-surface productivity, desert extent and forest fires. Typical ice cores are removed from an ice sheet such as the ice cap internal to Greenland. Greenland is, by area, the world's largest island. The Greenland ice sheet covers about 1.71 million km2 and contains about 2.6 million km3 of ice.〔(【引用サイトリンク】title=NSIDC Arctic Sea Ice News Fall 2007 )〕 ==Greenland ice sheet== (詳細はice covering 1.71 million km2, roughly 80% of the surface of Greenland. It is the second largest ice body in the World, after the Antarctic Ice Sheet. The ice sheet is almost 2,400 kilometers long in a north-south direction, and its greatest width is 1,100 kilometers at a latitude of 77°N, near its northern margin. The mean altitude of the ice is 2,135 meters.〔Encyclopaedia Britannica. 1999 Multimedia edition.〕 The ice in the current ice sheet is as old as 110,000 years.〔("The Summit Ice Cores (GISP2 and GRIP)" ). National Report to IUGG, Rev. Geophys. Vol. 33 Suppl., American Geophysical Union, 1995.〕 However, it is generally thought that the Greenland Ice Sheet formed in the late Pliocene or early Pleistocene by coalescence of ice caps and glaciers. It did not develop at all until the late Pliocene, but apparently developed very rapidly with the first continental glaciation. The ice surface reaches its greatest altitude on two north-south elongated domes, or ridges. The southern dome reaches almost 3,000 metres at latitudes 63°–65°N; the northern dome reaches about 3,290 metres at about latitude 72°N. The crests of both domes are displaced east of the centre line of Greenland. The unconfined ice sheet does not reach the sea along a broad front anywhere in Greenland, so that no large ice shelves occur. On the ice sheet, temperatures are generally substantially lower than elsewhere in Greenland. The lowest mean annual temperatures, about −31 °C (−24 °F), occur on the north-central part of the north dome, and temperatures at the crest of the south dome are about −20 °C (−4 °F). During winter, the ice sheet takes on a strikingly clear blue/green color. During summer, the top layer of ice melts leaving pockets of air in the ice that makes it look white. Positioned in the Arctic, the Greenland ice sheet is especially vulnerable to global warming. Arctic climate is now rapidly warming. 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「Dye 3」の詳細全文を読む スポンサード リンク
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