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【引用】白令海峡的水位升降改变气候(图)  

2012-05-28 13:41:51|  分类: 天气学与气候背景 |  标签: |举报 |字号 订阅

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白令海峡的水位升降改变气候(图) - 月亮飞船 - 欢迎光临月亮飞船的博客

白令海峡在冰期期间好象能够调节海平面。

Bering Strait's Ups and Downs Alter Climate

By Phil Berardelli   胡德良

The Bering Strait, the 80-kilometer-wide stretch of ocean between Russia and Alaska, can strongly influence the climate of the entire Northern Hemisphere, researchers have calculated. The findings answer a question that has dogged scientists for the past decade, and they demonstrate how seemingly slight changes in certain factors can impact global climate.   

 研究人员通过计算发现,俄罗斯和阿拉斯加之间80公里宽的狭长海域——白令海峡可以严重地影响整个北半球的气候。该发现解决了在过去十年中一直困扰着科学家们的问题,证明了看似微小的变化在一定的因素条件下可以影响全球的气候。

 For the past several million years, Earth has been locked in a glacial cycle. Ice ages come and go with remarkable regularity, lasting 100,000 years or so and then letting up for 10,000 to 15,000 years. The last such ice age ended about 11,000 years ago. Within each ice age, the kilometer-thick ice sheets that cover much of the top of the world also go through cycles, thickening and thinning, extending and receding, over periods lasting a few thousand years. But until now, no one has been able to pinpoint the cause of these oscillations.

 在过去的几百万年中,地球被封锁在一种冰期旋回中。冰期的来去带有明显的规律性:冰期到来之后持续10万年左右,然后经历一个10,00015,000年的冰期中止期。最后一个这样的冰期是在大约11,000年前结束的。在每一个冰期内,覆盖着世界大部分地区的冰盖厚达几千米,也经历着周期性变化,时厚时薄,时进时退,一个周期可持续几千年。然而,此前没有人能够查明这些振荡的原因所在。

 This pressing question has now been tackled by Aixue Hu, an oceanographer at the U.S. National Center for Atmospheric Research in Boulder, Colorado, and colleagues. They studied the Bering Strait's potential impact on glacial oscillations. They knew that every so often during past ice ages, drops in sea level created a land bridge across the strait. By analyzing data from ocean sediments, Hu's team found that the timing of the bridge's appearance seemed to be linked to the oscillations of the ice sheets. So the researchers combined the ocean sediment data with calculations of Earth's orbital and rotational variations--which are known to trigger or end the ice ages--into a new supercomputer model. As they report online this week in Nature Geoscience, the model shows that the Bering Strait's status was directly responsible for the ice-sheet oscillations.

 现在,科罗拉多州博尔德市美国国家大气研究中心的海洋学家胡爱学及同事解决了这个紧迫的问题。他们研究了白令海峡对冰期振荡的潜在影响。在最后一个冰期期间,他们了解到海平面的下降偶尔会产生横跨海峡的陆桥。通过对海洋沉积物的数据分析,胡爱学的研究小组发现陆桥出现的时期好象跟冰盖的振荡相关。因此,研究人员将海洋沉积物数据跟地球轨道和旋转变化的数据结合起来,一并输入到一台超级计算机模型中。据了解,地球轨道和旋转的变化会引发或中止冰期。他们在本周《自然-地球科学》杂志在线版上报道:模拟显示,白令海峡的状况是造成冰盖振荡的直接原因。

 Based on the model, this is what happens. At the beginning of an ice age, massive sheets of ice build up and advance across North America, Greenland, Europe, and northern Asia. These sheets sequester a great deal of water, causing sea levels to plunge and exposing the land bridge across the Bering Strait. When the strait closes, water cannot flow from the Pacific Ocean into the Arctic Ocean. The loss of that inflow means saltier--and warmer--water from the Atlantic Ocean has an easier path into the Arctic. The warmer water melts the ice sheets around their edges, which in turn floods the Arctic and Atlantic oceans with fresh water, raising sea levels again and moderating the northern climate. Once the seas are high enough, the Bering Strait reopens, cold Pacific water reenters the Arctic, the climate cools enough for the ice sheets to advance, and the whole process repeats.

 根据此次模拟,所发生的情况是这样的:在冰期开始之时,大量的冰盖积累起来,蔓延到北美、格陵兰、欧洲和亚洲北部地区,这些冰盖阻断了大量的水源,引起海平面下降,横跨白令海峡的陆桥显露出来,这时海峡封闭,水无法从太平洋流入北冰洋;太平洋水无法流入,意味着含盐量较大、温度较高的大西洋水更容易进入北极地区,温度较高的水融化了周边的冰盖,融化的冰盖反过来又为北冰洋和大西洋注入了大量的淡水,结果使得海平面再次升高,同时也缓和了北半球的气候;一旦海平面升得足够高之后,白令海峡再次畅通,寒冷的太平洋水重新流进北冰洋,气候变冷之后足以使冰盖蔓延。就这样整个过程重复不止。

 Still undetermined, Hu says, is exactly where and how the warming waters interact with the ice sheets. Finding that out is going to require a new generation of models, he adds.

 胡爱学说:温暖的水域到底在哪里与冰盖交汇,又是如何交汇的,这些情况尚不确定。他又说道,要想搞清这些情况将需要新一轮的模拟。

 Fluid dynamicist Ronald Stouffer of the National Oceanic and Atmospheric Administration in Princeton, New Jersey, agrees. A full understanding of the process described in the paper will have to wait until a comparable ice-sheet model can be developed, he says. Nevertheless, the research improves our understanding of past climate variations "and therefore gives us more confidence in future projections."

 新泽西州普林斯顿市国家国家海洋和大气管理局的流体力学家罗纳德·斯托佛同意胡爱学的观点。他说,要想完全了解论文中描述的过程,将不得不等待开发一个相当的冰盖模型。然而,该研究增进了我们对以往气候变化的认识,因此使我们对今后的预测更加有信心。

译自:美国《科学》杂志网站(11 January 2010

原著:Phil Berardelli

欢迎光临我博:http://huzhangao.blog.163.com/

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