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Scientists unveiled on Sunday the first direct evidence that massive floods deep below Antarctica's ice cover are accelerating the flow of glaciers into the sea.
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Scientists unveiled on Sunday the first direct evidence that massive floods deep below Antarctica's ice cover are accelerating the flow of glaciers into the sea.
How quickly these huge bodies of ice slide off the Antarctic and Greenland land masses into the ocean help determine the speed at which sea levels rise.
The stakes are enormous: An increase measured in tens of centimeters could wreak havoc for hundreds of millions of people living in low-lying deltas and island nations around the world.
Researchers discovered only recently that inaccessible subglacial lakes in Antarctica periodically shed huge quantities of water.
Data collected by a satellite launched in 2003 - the Ice, Cloud and Land Elevation Satellite, or ICESat - revealed a complex network of subglacial plumbing in which water periodically cascades from one hidden reservoir to another.
But the new study, published online in the journal Nature Geoscience, is the first to measure the potential impact of this invisible flooding on sea-bound glaciers.
A trio of scientists led by Leigh Stearns of the Climate Change Institute at the University of Maine matched ICESat data against a nearly 50-year record of how fast the Byrd Glacier in East Antarctica has moved toward the sea.
They discovered that during the same 14-month period that 1.7 cubic km of water cascaded through subglacial waterways, the 75-km long glacier downstream pick up speed, moving about 10 percent faster.
"Our findings provide direct evidence that an active lake drainage system can cause large and rapid changes in glacier dynamics," the researchers concluded.
"Water acts as a lubricant, reducing friction at the base of the ice and making ice flow faster," explained Helen Fricker of the Scripps Institution of Oceanography of California in a commentary, also in Nature Geoscience.
The study adds to growing scientific concern about the pace at which glaciers are melting into the seas.
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(Agencies)
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科學(xué)家于上周日首次公布資料，證明南極冰層下的大規(guī)模水流正加速冰川流向海洋。
這些體積龐大的冰川正從南極大陸和格陵蘭島漂向海洋，它們漂移的速度直接決定了海平面升高的速度。
這導(dǎo)致的后果將觸目驚心：海平面升高幾十厘米就足以威脅居住在地勢(shì)較低的三角洲及島國(guó)地區(qū)的億萬(wàn)人民的生存。
研究人員最近發(fā)現(xiàn)，南極冰層下隱秘的湖泊會(huì)發(fā)生周期性的傾瀉。
美國(guó)宇航局2003年發(fā)射的“冰云和地面高度衛(wèi)星”（ICESat）收集的數(shù)據(jù)顯示，南極冰層下有一個(gè)復(fù)雜的湖泊排水網(wǎng)絡(luò)，湖水會(huì)周期性地從一個(gè)隱秘的湖泊流向另一個(gè)湖泊。
而這項(xiàng)最新研究則首次估量了海洋冰川下隱秘水流的潛在影響。該研究成果在《自然地學(xué)》期刊的網(wǎng)絡(luò)版上發(fā)表。
以美國(guó)緬因州大學(xué)氣候變化學(xué)院的斯特恩斯為首的三位科學(xué)家將衛(wèi)星數(shù)據(jù)與南極東部的伯德冰川在過(guò)去近50年中移向海洋的速度進(jìn)行了對(duì)比。
通過(guò)比較，研究人員發(fā)現(xiàn)，在14個(gè)月的時(shí)間中，冰層下湖泊溢出了1.7立方千米的水，75公里長(zhǎng)的伯德冰川的移動(dòng)速度加快了10%。
研究人員由此得出結(jié)論：“活躍的湖泊排水系統(tǒng)會(huì)導(dǎo)致冰川運(yùn)動(dòng)出現(xiàn)大規(guī)模、快速的變化，我們的研究結(jié)果為此提供了直接證據(jù)。”
加州斯克里普斯海洋學(xué)研究所的海倫?弗里克在一篇科學(xué)評(píng)論中解釋說(shuō)：“水可起到潤(rùn)滑劑的作用，減少了冰層底部的摩擦，所以加速了冰川的流動(dòng)。”她的這篇文章也在《自然地學(xué)》期刊上發(fā)表。
該研究進(jìn)一步加劇了科學(xué)家對(duì)冰川融化速度的擔(dān)憂。
（實(shí)習(xí)生許雅寧 英語(yǔ)點(diǎn)津姍姍編輯）
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