|
Drift ice is any sea ice other than fast ice, the latter being attached ("fastened") to the shoreline or other fixed objects (shoals, grounded icebergs, etc.).〔〔Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer-Verlag.〕 Drift ice is carried along by winds and sea currents, hence its name. When drift ice is driven together into a large single mass (>70% coverage), it is called pack ice. Wind and currents can pile up that ice to form ridges up to several metres in height. These represent a challenge for icebreakers and offshore structures operating in cold oceans and seas. Drift ice consists of ''floes'', individual pieces of sea ice or more across. There are names for various floe sizes: ''small'' – to ; ''medium'' – to ; ''big'' – to ; ''vast'' – to ; and ''giant'' – more than . Seasonal ice drift in the Sea of Okhotsk by the northern coast of Hokkaidō, Japan has become a tourist attraction of this area with harsh climate,〔("A Port's Ice Is Thinning, and So Is Its Tourist Trade" ), ''New York Times'', March 14, 2006.〕 and is one of the 100 Soundscapes of Japan. The Sea of Okhotsk is the southernmost area in the Northern hemisphere where drift ice may be observed.〔(Honda, Meiji, Koji Yamazaki, Hisashi Nakamura, Kensuke Takeuchi, 1999: Dynamic and Thermodynamic Characteristics of Atmospheric Response to Anomalous Sea-Ice Extent in the Sea of Okhotsk. J. Climate, 12, 3347–3358. )〕 Drift ice affects: * Security of navigation * Climatic impact (see Polar ice packs) * Geological impact * Biosphere influence (see Ecology of sea ice) The two major ice packs are the Arctic ice pack and the Antarctic ice pack. The most important areas of pack ice are the polar ice packs formed from seawater in the Earth's polar regions: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean. Polar packs significantly change their size during seasonal changes of the year. Because of vast amounts of water added to or removed from the oceans and atmosphere, the behavior of polar ice packs has a significant impact on global changes in climate. ==See also== *Iceberg *Ice drift *Ice shove *Lead (sea ice) *Polar ice packs *Polynya *Pressure ridge (ice) *Seabed gouging by ice *Sea ice *Shelf ice *Soviet and Russian manned drifting ice stations 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「Drift ice」の詳細全文を読む スポンサード リンク
|