這一洋流有時被稱作為北大西洋傳送器。



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Mississippi River

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Is Earth's climate vulnerable to small disturbances? Two geologists writing in Scientific American described the past vulnerability of an ocean current sometimes called the North Atlantic conveyor. The conveyor works like this. At about 2,000 feet beneath the surface of the Atlantic Ocean extra-salty water flows northward from the tropics. Winds over the North Atlantic sweep surface water aside, allowing this warm salty water to rise to the surface and come into contact with the cold air. Heat passes from the water to the air. The extra-salty water, now extra-dense because it is only a few degrees above freezing, sinks to near the bottom of the Atlantic and flows southward around Africa. Meanwhile, the warmed air passes over Europe and makes European winters warmer than they would be otherwise. During a one-thousand-year period about 11,000 years ago, this conveyor was shut down, because the North Atlantic was flooded with melt water from Canadian glaciers. Previously, that melt water had flowed down the Mississippi River. But at some point the retreat of the glaciers opened a channel to the east.
地球的氣候是否傾向于小的不穩(wěn)定?兩位地質(zhì)學家在科學美國人上描述了一洋流過去的不穩(wěn)定性,這一洋流有時被稱作為北大西洋傳送器。 這一傳送裝置的工作原理是這樣的。在大西洋表面大約2000尺左右有一股咸度較高的水流從回歸線向北流動。北大西洋上的海風將表面的海水吹向一邊,以使這一溫暖的咸度較高的海水上升到海面并與較冷的空氣接觸。 熱量從海水傳到空氣中。咸度較高的海水,現(xiàn)在因為溫度只在冰點以上幾度而變的密度非常高,下沉到大西洋的底部,洋流在非洲附近向南流動。于此同時,溫暖的空氣經(jīng)過歐洲使得歐洲的冬天比應該的要暖的多。 在過去的1000年到大約11000之間,這一傳送帶處于關閉狀態(tài),因為北大西洋注滿了從加拿大冰川融化的水。以前,這些融化的水是應該流入密西西比河的。但是在一些情況下融化的冰川開通了往東的河道。