VOA标准英语2012--Ocean Floor Reveals Past Climate Changes

Ocean Floor Reveals Past Climate Changes

Time capsule
Lamont research professor Maureen Raymo, the director of the Core Repository, slides open a long, narrow drawer from the cabinet. Like thousands of others here, the drawer contains a long, thin cylinder¹ of layered sediment².
It’s a sample extracted from the ocean floor and below. According to Raymo, the cylinder’s distinctive³ stripes of varied⁴ colors and widths are a unique visual record, a sort of vertical⁵ time capsule.
“Imagine you are out on a boat, and you could see right through the four kilometers of water that is between you and the bottom. And on the bottom all the little fossils, all the little plankton⁶ that die over the years in the water column, their remains⁷ settled to the sea floor, just gently settled to the bottom," Raymo says. "And they accumulate, layer by layer by layer, over millions of years. So imagine you just came along and just stuck a big piston⁸ tube into the sediment, or took a straw and stuck it into the sediment and pushed it 20 meters down and extracted it, you would have a long core that would essentially⁹ be a record of sedimentation¹⁰ going back in time. For geologists¹¹, it’s the equivalent of a tape recorder.”
Invaluable¹² resource
Lamont-Doherty oceanographic vessels¹³ started collecting these samples more than 50 years ago, at a time when no one was sure what they would be used for.
“The first director, Maurice Ewing, had the sense that these cores had to contain important information and it turns out they do," Raymo says. "They’ve been an invaluable resource in studying past climate change, past ocean circulation, past ocean temperatures, the evolution of life in the ocean in the past, and they are an incredible archive of the evolution of life in the ocean in the past.”
The core samples provide a reliable record partly because the deep ocean is a very peaceful place, compared to the shoreline.
“It’s very far away from the margins¹⁴ where there is a lot of erosional material coming in, where there are lots of waves breaking on the shores and on the continental¹⁵ shelf. Material that settles through the water column just gently layers on the bottom, layer by layer by layer, and it can just be undisturbed for millions of years.”
Vital clues
According to Raymo, the types of species one finds along a length of core reveal vital clues about past environmental changes where the sample was taken. She asks us to imagine a core sample from the middle of the North Atlantic Ocean:
“And you go down your core and you see these kind of sub-polar species, temperate¹⁶ species. Then all of a sudden, you see species that only live in sea ice or next to sea ice. And that tells you that at that location, at that time in the past, sea ice covered that part of the North Atlantic. Because you only see these polar species of plankton. You could go further south and look at a core and see it varying between tropical species and subtropical species, and that’s directly reflective of how the sea surface temperature was changing through time.”
Looking at climate changes of the past helps scientists understand the changes the earth is undergoing today, and is nearly certain to experience at an accelerated rate in the future. Raymo says that when she was a doctoral student in the 1980s, climate change was an esoteric subject few considered relevant.
“And now it’s obviously incredibly relevant. Humans are changing the atmosphere in profound ways by increasing greenhouse gases, and climate is responding to that. The earth is warming. And so there are a lot of questions about how high can CO2 go without causing fairly devastating¹⁷ changes in global climate, either through sea level rise as ice sheets melt, changing precipitation patterns.... And the people in my field, we really look it at as ‘the past is the key to the future’ here.”

1 cylinder   

n.圆筒，柱(面)，汽缸

参考例句：

• What's the volume of this cylinder?这个圆筒的体积有多少？
• The cylinder is getting too much gas and not enough air.汽缸里汽油太多而空气不足。

2 sediment   

n.沉淀，沉渣，沉积(物)

参考例句：

• The sediment settled and the water was clear.杂质沉淀后，水变清了。
• Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。

3 distinctive   

adj.特别的，有特色的，与众不同的

参考例句：

• She has a very distinctive way of walking.她走路的样子与别人很不相同。
• This bird has several distinctive features.这个鸟具有几种突出的特征。

4 varied   

adj.多样的，多变化的

参考例句：

• The forms of art are many and varied.艺术的形式是多种多样的。
• The hotel has a varied programme of nightly entertainment.宾馆有各种晚间娱乐活动。

5 vertical   

adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置

参考例句：

• The northern side of the mountain is almost vertical.这座山的北坡几乎是垂直的。
• Vertical air motions are not measured by this system.垂直气流的运动不用这种系统来测量。

6 plankton   

n.浮游生物

参考例句：

• Plankton is at the bottom of the marine food chain.浮游生物处于海洋食物链的最底层。
• The plankton in the sea feeds many kinds of animals. 海的浮游生物成为很多种动物的食物。

7 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

8 piston   

n.活塞

参考例句：

• They use a piston engine instead.他们改用活塞发动机。
• The piston moves by steam pressure.活塞在蒸汽压力下运动。

9 essentially   

adv.本质上，实质上，基本上

参考例句：

• Really great men are essentially modest.真正的伟人大都很谦虚。
• She is an essentially selfish person.她本质上是个自私自利的人。

10 sedimentation   

n.沉淀，沉积

参考例句：

• Sedimentation, the damage of a breach are problems, too. 而且沉积和决口的问题，也是存在的。 来自英语晨读30分（高二）
• Sedimentation and denudation play a role in exceptional cases. 沉积和剥蚀作用的影响只在特殊情况下起作用。

11 geologists   

地质学家，地质学者( geologist的名词复数 )

参考例句：

• Geologists uncovered the hidden riches. 地质学家发现了地下的宝藏。
• Geologists study the structure of the rocks. 地质学家研究岩石结构。

12 invaluable   

adj.无价的，非常宝贵的，极为贵重的

参考例句：

• A computer would have been invaluable for this job.一台计算机对这个工作的作用会是无法估计的。
• This information was invaluable to him.这个消息对他来说是非常宝贵的。

13 vessels   

n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人

参考例句：

• The river is navigable by vessels of up to 90 tons. 90 吨以下的船只可以从这条河通过。 来自《简明英汉词典》
• All modern vessels of any size are fitted with radar installations. 所有现代化船只都有雷达装置。 来自《现代汉英综合大词典》

14 margins   

边( margin的名词复数 )； 利润； 页边空白； 差数

参考例句：

• They have always had to make do with relatively small profit margins. 他们不得不经常设法应付较少的利润额。
• To create more space between the navigation items, add left and right margins to the links. 在每个项目间留更多的空隙，加左或者右的margins来定义链接。

15 continental   

adj.大陆的，大陆性的，欧洲大陆的

参考例句：

• A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
• The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。

16 temperate   

adj.温和的，温带的，自我克制的，不过分的

参考例句：

• Asia extends across the frigid,temperate and tropical zones.亚洲地跨寒、温、热三带。
• Great Britain has a temperate climate.英国气候温和。

17 devastating   

adj.毁灭性的，令人震惊的，强有力的

参考例句：

• It is the most devastating storm in 20 years.这是20年来破坏性最大的风暴。
• Affairs do have a devastating effect on marriages.婚外情确实会对婚姻造成毁灭性的影响。