An iceberg's crash into an Antarctic glacier last year cracked off a huge swathe of ice, bringing to light a vast span of the Southern Ocean and providing scientists with a chance to conduct experiments that may help understand climate change. The incident, in which the iceberg clipped the Mertz Glacier in East Antarctica and broke off nearly 78 kilometers of glacier tongue, exposed a section of ocean water previously covered in hundreds of meters of ice and brought to light marine life including sea stars as big as hubcaps. "Suddenly the geometry of Antarctica has changed," said Steve Rintoul, an oceanographer with the Antarctic Climate and Ecosystems Cooperative Research Center at CSIRO in Tasmania. A team of 40 Australian and international scientists, including Rintoul, visited the region during the Antarctic summer to study the impact of the calving. Among the unanticipated biological results was the release of about 10,000 square meters of ice into the ocean when it drifted off into warmer water. The consequent melting ice decreased water salinity and sparked an intense bloom of phytoplankton. The plants need light and nutrients to grow, along with small amounts of iron that usually comes as dust falling from the sky. "The old ice had accumulated decades of iron dust supply, and when it broke off and melted it seems to have provided the phytoplankton with between 20 and 40 years' dose of iron in a single season," Rintoul said. Another side effect, combined with clearer water, was the exposure of sea animals including giant sea stars, colorful sponges and feathery sea pens, revealed after decades in dark Antarctic waters. "Some of the areas we sampled have been under ice for many decades that no ship has ever reached that area," Rintoul explained. Overall, researchers ended up with an unprecedented chance to test theories of how the marine ecosystem might respond to such large-scale changes, a possible foretaste of what could lie ahead with climate change. "It was a sort of natural experiment, where the calving of the glacier tongue was not caused by climate change. This is a natural event, so nature has done the experiment for us this time," he concluded. 這座冰山撞上南極東部的默茨冰川，導致將近七十八公里的冰舌崩落。這讓過去覆蓋於數百公尺冰層底下的一部分海洋曝光，宛如汽車殼蓋大的海星等海洋生物也因而現蹤。 澳洲科學與工業研究組織中的南極氣候與生態系合作研究中心的海洋學家史提夫林圖爾表示：「南極的結構突然之間改變了。」該研究中心位於塔斯馬尼亞島。 包括林圖爾等一共四十位澳洲與世界各國的科學家組成了一個團隊，他們在南極夏季時走訪當地，研究冰川崩解帶來的衝擊。 當一萬平方公尺左右的冰漂到較溫暖的水域後，進入了海洋。這便是其中一個會對生物造成影響的狀況，但先前卻沒料到。 隨後融解的冰層減少了海水的鹹度，使浮游植物群落大量生長。這種植物需要陽光、營養以及通常來自於天空中飄落塵埃的少許鐵才能生長。 林圖爾指出：「古老的冰層累積了數十年的鐵屑。當冰層崩解與融化後，似乎能在一個季節為浮游植物群落提供廿至四十年的鐵含量。」 隨著海水見世，也帶來了另一項副作用。包括巨大水星、色彩斑斕的海棉以及如羽毛似的海筆等海中生物，數十年載都生活在黑暗的南極水域中，不過現在終於曝了光。 林圖爾解釋：「我們調查過的部分區域，好幾十年來都被冰層覆蓋，因此從來沒有船隻到過那些地方。」 總體而言，研究人員獲得了空前的大好機會，可以測試海洋生態系統或許會如何回應如此大規模轉變的理論，這也可能預測氣候變遷將來會帶來什麼樣的影響。 他最後表示：「這像一項大自然的實驗，因為冰舌的崩解並非氣候變遷所導致。這是自然事件，大自然這次為我們做了這個實驗。」 http://www.chinapost.com.tw/guidepost/topics/default.asp?id=2550&sub=2
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