2020年经济学人 北极探险(2)

And changing they are, for the extent of the Arctic sea ice in summer has declined by 30% in the past 30 years, and that loss is accelerating.

它们正在发生变化，因为在过去的30年里，北极海冰的面积在夏季减少了30%，而且减少的速度还在加快。

The Arctic is also a driver of climate change, though, because the whiteness of ice means it reflects sunlight back into space, thus cooling Earth,

北极区也是气候变化的推动者，冰的白度意味着它将太阳光反射回太空，从而给地球降温，

whereas the darkness of open water means it absorbs that light.

而无冰水面的暗度意味着它吸收了这个光。

The less of the former that is happening, and the more of the latter, the faster global temperatures will rise.

前一种情况发生得越少，后一种情况就越常见，全球气温上升的速度就会越快。

Start, then, with the ice. At the moment this is monitored mainly by satellite. Measuring the extent of the Arctic's ice from space is easy.

首先从冰开始。目前这主要是由卫星监测的。从太空测量北极冰的范围很容易。

Measuring its thickness is trickier¹. From orbit, this is done by a mixture of radar² and laser beam.

测量冰的厚度则更加棘手。在轨道上，这是由雷达和激光束共同完成的。

Icesat 2, an American craft, provides laser-altimeter data that record the height above sea level of the top of the snow that overlies the ice.

美国飞船Icesat 2提供激光高度计数据，该数据记录了覆盖在冰层的雪顶的海拔标高。

Cryosat 2, a European one, uses radar to penetrate³ the snow and measure the height of the top of the ice itself.

欧洲飞船Cryosat 2使用雷达穿透积雪并测量冰顶部本身的高度。

The thickness of the ice in a particular place can then be calculated by applying Archimedes' principle of floating bodies to the mixture of ice and snow,

将阿基米德的浮体原理应用于冰雪混合中，然后减去雪的厚度，

and subtracting the thickness of the snow. However, Julienne Stroeve of University College London, now safely returned from her leg of the mission,

就可以计算出某个地方冰的厚度。但英国伦敦大学学院的Julienne Stroeve（现在她已经从任务中安全返回）

believes that the data collected by these two satellites may be inaccurate⁴, leading to an overestimation⁵ of the ice's thickness.

认为这两个卫星所收集的数据可能不准确，从而导致对冰厚度评估过高。

When all is working perfectly⁶, the return signal for Cryosat 2 comes exactly from the boundary between the ice and any overlying snow.

当一切正常运行时，Cryosat 2的返回信号就会准确地从冰和覆盖积雪的边界传回来。

Dr Stroeve thinks, though, that this is not always what happens.

但Stroeve博士认为情况并非总是如此。

Variables such as layering within the snow, along with its temperature and salinity⁷,

雪中的分层、温度和盐度等变量，

might affect the returning radar signal by changing the snow's structure and density⁸.

可能会改变雪的结构和密度，从而影响返回的雷达信号。

This could cause the signal to be reflected from inside the snow layer, rather than from the boundary where it meets the ice.

这可能会导致信号从雪层内部反射，而不是从它与冰接触的边界反射。

If that were happening, it would create the illusion that the ice beneath the snow is thicker than is actually the case.

如果这种情况真的发生了，就会产生一种错觉，即雪下的冰比实际情况要厚。

To investigate this possibility Dr Stroeve took a purpose-built radar on board Polarstern.

为了调查这种可能性，Stroeve博士将一个特制的雷达带上了极星号。

Each week, she and a colleague mounted this 170kg instrument on a sled and dragged it to a new site, to sample different snow conditions.

每周，她和一名同事将这个170公斤重的仪器安装在一个雪橇上，拖到一个新的地点，以采样不同的雪况。

As they towed it, they sent radar pulses on the frequency bands used by the satellites downwards⁹ into the snow and measured the amount of backscatter.

当他们拖着雪橇的时候，他们在卫星使用的频段向雪中发射雷达脉冲，并测量反向散射的数量。

The deflection of the signals in this backscatter gives a picture of how particular snow conditions might be changing the way the satellite's radar is returned.

散射中信号的偏差说明了特定的雪况可能会如何改变卫星雷达返回的方式。

Dr Stroeve's radar died on January 31st— one of many of the expedition's machines that fell victim to the Arctic winter.

Stroeve博士的雷达损坏于1月31日——这是牺牲于北极冬季的众多探险设备中的一个。

But by the time that had happened she had managed to gather a fairly good set of data.

但当这一切发生时，她已经设法收集到了一组相当好的数据。

Her conclusion is that the reflection does indeed sometimes come from the interface¹⁰ between snow and ice, as it is supposed to. But not always.

她的结论是反射有时确实是来自雪和冰的接触面，应该如此，但不常发生。

The discrepancy¹¹ is important. Her measurements already show that the ice is "definitely thinner than the satellites suggested".

这种差异很重要。她的测量结果已经表明，冰层“肯定比卫星预测的要薄”。

She has yet to analyse the data fully¹², but preliminary investigation¹³ indicates that both snow depth and temperature influence backscatter.

她还没有充分分析数据，但初步调查表明，雪的深度和温度都会影响后向散射。

It therefore looks likely that the amount of Arctic sea ice around has been overestimated¹⁴.

因此，周围北极海冰的数量似乎被高估了。

1 trickier   

adj.狡猾的( tricky的比较级 )；（形势、工作等）复杂的；机警的；微妙的

参考例句：

• This is the general rule, but some cases are trickier than others. 以上是一般规则，但某些案例会比别的案例更为棘手。 来自互联网
• The lower the numbers go, the trickier the problems get. 武器的数量越低，问题就越复杂。 来自互联网

2 radar   

n.雷达，无线电探测器

参考例句：

• They are following the flight of an aircraft by radar.他们正在用雷达追踪一架飞机的飞行。
• Enemy ships were detected on the radar.敌舰的影像已显现在雷达上。

3 penetrate   

v.透(渗)入；刺入，刺穿；洞察，了解

参考例句：

• Western ideas penetrate slowly through the East.西方观念逐渐传入东方。
• The sunshine could not penetrate where the trees were thickest.阳光不能透入树木最浓密的地方。

4 inaccurate   

adj.错误的，不正确的，不准确的

参考例句：

• The book is both inaccurate and exaggerated.这本书不但不准确，而且夸大其词。
• She never knows the right time because her watch is inaccurate.她从来不知道准确的时间因为她的表不准。

5 overestimation   

[经] 过高的估计

参考例句：

• Oppose overestimation of the enemy's strength. 反对对敌人的力量估计过高。

6 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。

7 salinity   

n.盐分；咸度；盐浓度；咸性

参考例句：

• In the sea water sampled the salinity is two parts per thousand.在取样的海水中，盐度为千分之二。
• In many sedimentary basins the salinity of the formation water increases with depth or compaction.在许多沉积盆地中，地层水的含盐量随深度或压实作用而增高。

8 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。

9 downwards   

adj./adv.向下的（地），下行的（地）

参考例句：

• He lay face downwards on his bed.他脸向下伏在床上。
• As the river flows downwards,it widens.这条河愈到下游愈宽。

10 interface   

n.接合部位，分界面；v.(使)互相联系

参考例句：

• My computer has a network interface,which allows me to get to other computers.我的计算机有网络接口可以与其它计算机连在一起。
• This program has perspicuous interface and extensive application. 该程序界面明了，适用范围广。

11 discrepancy   

n.不同；不符；差异；矛盾

参考例句：

• The discrepancy in their ages seemed not to matter.他们之间年龄的差异似乎没有多大关系。
• There was a discrepancy in the two reports of the accident.关于那次事故的两则报道有不一致之处。

12 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

13 investigation   

n.调查，调查研究

参考例句：

• In an investigation,a new fact became known, which told against him.在调查中新发现了一件对他不利的事实。
• He drew the conclusion by building on his own investigation.他根据自己的调查研究作出结论。

14 overestimated   

对（数量）估计过高，对…作过高的评价( overestimate的过去式和过去分词 )

参考例句：

• They overestimated his ability when they promoted him. 他们提拔他的时候高估了他的能力。
• The Ministry of Finance consistently overestimated its budget deficits. 财政部一贯高估预算赤字。