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In Greenland, Ice and Instabilit

游客2023-12-28  11
问题                                                 In Greenland, Ice and Instability
    The ancient frozen dome cloaking Greenland is so vast that pilots have crashed into what they thought was a cloud bank spanning the horizon. Flying over it, you can scarcely imagine that it could erode fast enough to dangerously raise sea levels any time soon.
    Along the flanks in spring and summer, however, the picture is very different. For an increasing number of warm years, a network of blue lakes and rivulets of melt-water has been spreading ever higher on the icecap.
    The melting surface darkens, absorbing up to four times as much energy from the sun as snow, which reflects sunlight. Natural drainpipes called moulins carry water from the surface into the depths, in some places reaching bedrock.
    The process slightly, but measurably, lubricates and accelerates the grinding passage of ice towards the sea.
    Most important, many glaciologists say, is the break-up of huge semi-submerged clots of ice where some large Greenland glaciers, particularly along the west coast, squeeze through fiords as they meet the warming ocean. As these passages have cleared, this has sharply accelerated the flow of many of these creeping, corrugated and frozen rivers.
    Some glaciologists fear that the rise in seas in a warming world could be much greater than the upper estimate of about 60 centimetres this century made by the Intergovernmental Panel on Climate Change last year. (Seas rose less than 30 centimetres last century.)
    The panel’ s assessment did not include factors known to contribute to ice flows but not understood well enough to estimate with confidence. SCIENTIFIC scramble is under way to clarify whether the erosion of the world’ s most vulnerable ice sheets, in Greenland and west Antarctica, can continue to accelerate. The effort involves field and satellite analyses and sifting for clues from past warm periods.
    Things are definitely far more serious than anyone would have thought five years ago.
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答案     格林兰岛被广袤的原始冰层所笼罩，飞行员曾将冰层误认为地平线上隆起的云堤迎头相撞。飞越冰岛，你很难想象冰层被侵蚀的速度会如此之快，似乎冰岛随时都有被海水淹没的危险。
    值初春夏末之际，格陵兰岛却呈现出一幅截然不同的景象。由于连续多年气候变暖，蓝色湖泊与融水溪流交织的水网在冰盖之上越漫越广。
    积雪可折射太阳光，而融化处表面的颜色变深，吸收的太阳热量是积雪表面吸收热量的四倍。冰臼像天然的排水管道将融化的雪水从表面灌向底层，有些区域一直通向基岩。
    这一过程对冰层向海水的倾斜起到催化加速的作用。进程虽然缓慢，但却视之可见。
    多名冰川学家称，最严重的问题是，因遇到海洋暖流，格林兰岛上的大块冰山挤过海湾之时，会引发大块半漂浮冰层的断裂，尤其是在西部沿海区域。冰山活动明显，极大地为诸多蜿蜒褶皱的冰流推波助澜。
    部分冰川学家担心，全球变暖环境下，海平面上升的高度将远远超过政府间气候变化专门委员会去年预测的涨幅上限—60厘米。（上世纪，海平面已上涨近30厘米。）
    专家委员会的评估中没有涵盖所有已知的影响冰川流动的因素，也没有充分掌握如何进行准确评估的方法。目前正有科学研究对格林兰岛和南极大陆上最薄弱的冰层予以观察，以弄清楚冰层的侵蚀现象是否会继续加快。研究包括现场和卫星勘测分析以及对历史阶段变暖时期研究纪录的筛查。
    与五年之前人们的预想相比，显而易见，目前事态更加严重。
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