How we look kilometers below the Antarctic ice sheet | Dustin Schroeder

翻译人员: Chen Zou 校对人员: Yolanda Zhang

I'm a radio glaciologist.

我是一个雷达冰川学家。

That means that I use radar to study glaciers and ice sheets.

也就是说我用雷达 研究冰川和冰层。

And like most glaciologists right now,

就像现在大部分的冰川学家，

I'm working on the problem of estimating

我在研究预估

how much the ice is going to contribute to sea level rise in the future.

有多少冰将会在未来 引起海面上升的问题。

So today, I want to talk to you about

今天，我想和你们探讨

为什么为海平面上升做出 一个准确的预估是如此之难，

why it's so hard to put good numbers on sea level rise,

and why I believe that by changing the way we think about radar technology

以及为什么我相信通过改变 我们思考雷达技术的方式

and earth-science education,

以及地球科学教育，

we can get much better at it.

我们可以有更好的进展。

When most scientists talk about sea level rise,

当大部分的科学家 谈论起海平面上升的时候，

they show a plot like this.

通常会展示一张这样的图。

This is produced using ice sheet and climate models.

这是基于冰层 和气候模型制作出来的。

On the right, you can see the range of sea level

在右边，你可以看到 用这些模型预测出的

predicted by these models over the next 100 years.

未来一百年的 海平面高度范围。

For context, this is current sea level,

我来解释一下，这是现今的海平面，

and this is the sea level

而这个地方的数值意味着

above which more than 4 million people could be vulnerable to displacement.

海平面上升到这个位置以上， 就有四百多万人口面临迁移。

So in terms of planning,

那么，就计划来说，

the uncertainty in this plot is already large.

这个版本的不确定性已经很大了。

However, beyond that, this plot comes with the asterisk and the caveat,

然而除此之外，这个版本 还附带着星号和警告，

"... unless the West Antarctic Ice Sheet collapses."

“。。。除非西南极的冰层坍塌。”

And in that case, we would be talking about dramatically higher numbers.

在那种情况下，我们将会讨论 异常高的数字。

They'd literally be off the chart.

它们可以超出这张表的范围以外了。

And the reason we should take that possibility seriously

我们应该重视 那个可能性的原因

is that we know from the geologic history of the Earth

是我们知道从地球的 地理学历史角度来看，

that there were periods in its history

在历史中有这么一段时期，

when sea level rose much more quickly than today.

海平面上升得比现今快得多。

And right now, we cannot rule out

现在，我们不能够排除

the possibility of that happening in the future.

那个可能性会在未来出现的情况。

So why can't we say with confidence

那么为什么我们无法确认，

whether or not a significant portion of a continent-scale ice sheet

是否很大一部分大陆面积的冰层

将会，或者将不会坍塌？

will or will not collapse?

Well, in order to do that, we need models

要做到这一点，我们需要

that we know include all of the processes, conditions and physics

能包括像那样的坍塌中会出现的

that would be involved in a collapse like that.

所有的过程，条件和 物理原理的模型。

And that's hard to know,

那样的信息很难获取，

because those processes and conditions are taking place

因为这些过程和条件发生在

beneath kilometers of ice,

冰面下几公里的地方，

and satellites, like the one that produced this image,

卫星，比如说 制造这张图像的卫星

are blind to observe them.

是看不到它们的。

In fact, we have much more comprehensive observations of the surface of Mars

实际上相比起对 南极冰层以下的观察，

我们对火星表面的观察 倒还深入得多。

than we do of what's beneath the Antarctic ice sheet.

And this is even more challenging in that we need these observations

更富有挑战性的 是我们需要这些观察

在空间和时间上 都能达到一个庞大的规模。

at a gigantic scale in both space and time.

In terms of space, this is a continent.

就空间来说，这是一块大陆。

And in the same way that in North America,

和北美大陆一样，

the Rocky Mountains, Everglades and Great Lakes regions are very distinct,

落基山脉，弗罗里达州大沼泽， 还有五大湖地区都很特殊，

so are the subsurface regions of Antarctica.

南极表面区域也是一样。

And in terms of time, we now know

就时间而言，我们现在知道

that ice sheets not only evolve over the timescale of millennia and centuries,

冰层不仅仅以千年和百年的 时间跨度进化，

but they're also changing over the scale of years and days.

它们也在数年和数天的 时间跨度层面发生改变。

So what we want is observations beneath kilometers of ice

所以，我们想要的是在 一整个大陆范围内

at the scale of a continent,

对冰层下数公里的区域进行

and we want them all the time.

持续的观察。

So how do we do this?

那么我们怎么做到呢？

Well, we're not totally blind to the subsurface.

首先，我们不是完全 对表层一无所知的。

I said in the beginning that I was a radio glaciologist,

在一开始的时候我就说了， 我是一个无线电冰川学家，

and the reason that that's a thing

其背后的原因是

is that airborne ice-penetrating radar is the main tool we have

机载探冰雷达 是我们观察冰层内部时

to see inside of ice sheets.

所依赖的主要工具。

So most of the data used by my group is collected by airplanes

所以我们团队使用的大部分 数据是用飞机收集的，

like this World War II-era DC-3,

比如这种二战时期的DC-3，

that actually fought in the Battle of the Bulge.

它曾经参加过突出部之役。

You can see the antennas underneath the wing.

你可以看到在机翼下有天线。

These are used to transmit radar signals down into the ice.

这些天线被用来将雷达信号 传送到下面的冰层。

And the echos that come back contain information

传回的回声包含有关于

about what's happening inside and beneath the ice sheet.

在冰层内部和下面状况的信息。

While this is happening,

在这个过程中，

scientists and engineers are on the airplane

科学家和工程师在飞机上

for eight hours at a stretch,

要连续呆上8个小时，

making sure that the radar's working.

确保雷达运行正常。

And I think this is actually a misconception

我认为关于这类领域的工作

about this type of fieldwork,

存在一种误解，

人们想象着科学家俯视窗外，

where people imagine scientists peering out the window,

contemplating the landscape, its geologic context

琢磨着地理形状和结构

and the fate of the ice sheets.

以及冰层的命运。

We actually had a guy from the BBC's "Frozen Planet" on one of these flights.

曾经有一个BBC“冰冻地球”节目组的 报道员参与了一次我们的这种飞行，

And he spent, like, hours videotaping us turn knobs.

他录制了数小时的视频， 全都是我们在操作各种按钮。

(Laughter)

（观众笑声）

And I was actually watching the series years later with my wife,

数年之后我和我太太 一起观看这个系列报道，

and a scene like this came up, and I commented on how beautiful it was.

当这样的情景出现的时候， 我忍不住惊叹它的壮美。

And she said, "Weren't you on that flight?"

然后我太太说，“你难道不是在 那个飞机上吗？”

(Laughter)

（观众笑声）

I said, "Yeah, but I was looking at a computer screen."

我说，“是的，但是我一直在 盯着一个电脑屏幕。”

(Laughter)

（观众笑声）

So when you think about this type of fieldwork,

所以当你想到这种类型的 实地考察的时候，

don't think about images like this.

不要想着这样的景象。

Think about images like this.

你的脑海中应该出现这样的画面。

(Laughter)

（观众笑声）

This is a radargram, which is a vertical profile through the ice sheet,

这是一个雷达测绘图， 展现了冰层的垂直信息，

kind of like a slice of cake.

就像是一块蛋糕的截面。

The bright layer on the top is the surface of the ice sheet,

顶部比较亮的那一层 是冰层的表面，

the bright layer on the bottom is the bedrock of the continent itself,

底部比较亮的那一层 是大陆的基岩，

and the layers in between are kind of like tree rings,

中间像树的年轮一样 一层一层的，

in that they contain information about the history of the ice sheet.

里面包含着有关于冰层 历史的信息。

And it's amazing that this works this well.

令人惊喜的是，这个方法十分有效。

The ground-penetrating radars that are used

那些被用在调查道路

to investigate infrastructures of roads or detect land mines

基础设施或探测地雷的探地雷达

很难穿透至 地球以下的数米的位置。

struggle to get through a few meters of earth.

And here we're peering through three kilometers of ice.

这里我们可以投过冰层 观察三公里以下的信息。

And there are sophisticated, interesting, electromagnetic reasons for that,

这里有着复杂的 有趣的电磁方面的原因，

but let's say for now that ice is basically the perfect target for radar,

但是就现在来说，冰层基本上 对于雷达而言是完美的观测目标，

and radar is basically the perfect tool to study ice sheets.

而雷达基本上是 研究冰层的完美工具。

These are the flight lines

这些是在南极上空收集的

of most of the modern airborne radar-sounding profiles

大部分现代机载雷达探测资料的

飞行线。

collected over Antarctica.

This is the result of heroic efforts over decades

这是几十年来通过 由不同国家组成的团队

by teams from a variety of countries and international collaborations.

和国际合作实现的 英雄般努力的结果。

And when you put those together, you get an image like this,

当你把它们放在一起的时候， 就得到了像这样的图像，

which is what the continent of Antarctica would look like

那是南极大陆的真实图像，

在顶部没有冰层覆盖下的样貌。

without all the ice on top.

And you can really see the diversity of the continent in an image like this.

你真的可以在像这样的图片中 看到大陆的多样性。

The red features are volcanoes or mountains;

红色的特征代表着火山或是山川；

the areas that are blue would be open ocean

蓝色的区域是开放的海洋，

if the ice sheet was removed.

如果冰层被移掉的话。

This is that giant spatial scale.

这就是那种巨大的空间规模。

However, all of this that took decades to produce

然而，所有这些 花费了几十年时间打造的

is just one snapshot of the subsurface.

仅仅是表层的一个快照。

It does not give us any indication of how the ice sheet is changing in time.

它没有给我们任何关于冰层是如何 随着时间改变的暗示。

Now, we're working on that, because it turns out

目前，我们正致力于 这个方向的研究，因为我们发现

that the very first radar observations of Antarctica were collected

所收集的第一个对南极的雷达观测

using 35 millimeter optical film.

使用了35毫米的光学胶片。

And there were thousands of reels of this film

在剑桥大学史考特极地研究中心的

档案博物馆里还存留着

in the archives of the museum of the Scott Polar Research Institute

at the University of Cambridge.

上千个这套胶片的卷轴。

去年夏天，我使用了一个 很先进的用来电子化和

So last summer, I took a state-of-the-art film scanner

that was developed for digitizing Hollywood films and remastering them,

数位修复好莱坞电影的胶片扫描仪，

and two art historians,

并和两位艺术历史学家一起，

and we went over to England, put on some gloves

去了英格兰，戴上手套，

and archived and digitized all of that film.

数字化和备份了 那套胶片的所有信息。

So that produced two million high-resolution images

我们得到了两百万个 高清的图像，

that my group is now working on analyzing and processing

我的团队现在正在 分析和处理这些图像，

for comparing with contemporary conditions in the ice sheet.

进而与冰层的现状进行比较。

And, actually, that scanner -- I found out about it

实际上，那个扫描仪—— 我是从一个

from an archivist at the Academy of Motion Picture Arts and Sciences.

在美国电影艺术与科学学会 工作的档案师那里发现的。

So I'd like to thank the Academy --

所以，在这里我要感谢电影学会——

(Laughter)

（观众笑声）

for making this possible.

让这成为了可能 （模仿奥斯卡获奖感言）。

(Laughter)

（观众笑声）

And as amazing as it is

令人惊喜的是，

that we can look at what was happening under the ice sheet 50 years ago,

我们可以看到50年前 在冰层下所发生的一切，

this is still just one more snapshot.

虽然这仍然只是另一个快照。

It doesn't give us observations

它仍然没有给我们带来

of the variation at the annual or seasonal scale,

年度或季度层面 在多样性上的观察结果，

that we know matters.

而这些信息非常重要。

There's some progress here, too.

不过也有一些进展。

There are these recent ground-based radar systems that stay in one spot.

最近有一些地面雷达系统 可以停留在一点。

你将这些雷达放在冰层上，

So you take these radars and put them on the ice sheet

and you bury a cache of car batteries.

然后埋下一堆车载电池。

And you leave them out there for months or years at a time,

让它们在那里 一次性待上数月甚至数年，

然后隔几分钟，或者几个小时

and they send a pulse down into the ice sheet

就送一个脉冲到冰层内部。

every so many minutes or hours.

这样你就获得了一些 在时间上连续的观察——

So this gives you continuous observation in time --

but at one spot.

但只是针对一个点。

So if you compare that imaging to the 2-D pictures provided by the airplane,

如果你将那张图片和 由飞机提供的2D图片相比较，

this is just one vertical line.

这只是一条垂直的线。

And this is pretty much where we are as a field right now.

这就是我们现在在该 领域中所取得的进展。

We can choose between good spatial coverage

我们可以在好的空间覆盖

附加机载雷达探测，

with airborne radar sounding

and good temporal coverage in one spot with ground-based sounding.

和基于某一点的好的时间覆盖 附加地面雷达探测之间做出选择，

But neither gives us what we really want:

但这两个方法都不能 给我们想要的结果：

both at the same time.

两者在同时都没有。

And if we're going to do that,

如果我们要实现目标，

就需要用全新的方法去观察冰层。

we're going to need totally new ways of observing the ice sheet.

比较理想的情况下，这些方法 应该是非常低成本的，

And ideally, those should be extremely low-cost

so that we can take lots of measurements from lots of sensors.

让我们得以从很多的传感器上 获得大量的测量数据。

Well, for existing radar systems,

不过，对于现存的雷达系统来说，

最大的成本驱动 是能够让雷达系统自己

the biggest driver of cost is the power required

to transmit the radar signal itself.

发送雷达信号所需要的动力。

So it’d be great if we were able to use existing radio systems

所以如果我们能够利用 现有的无线电系统，

or radio signals that are in the environment.

或在环境中的无线电信号， 那就再好不过了。

And fortunately, the entire field of radio astronomy

幸运的是，整个 无线电天文领域都

is built on the fact that there are bright radio signals in the sky.

建立在天空中有很强的 无线电信号这一事实基础之上，

And a really bright one is our sun.

而最强烈最耀眼的那个 就是我们的太阳。

So, actually, one of the most exciting things my group is doing right now

实际上，我的团队正在做的 最令人激动的事情之一

就是试图使用来自太阳的 无线电发射送作为雷达信号的一种。

is trying to use the radio emissions from the sun as a type of radar signal.

This is one of our field tests at Big Sur.

这是我们在大苏尔地区进行的 实地测试中的一次。

That PVC pipe ziggurat is an antenna stand some undergrads in my lab built.

那个金字形神塔一样的PVC管道是由 我实验室的一些本科生搭建的天线架。

And the idea here is that we stay out at Big Sur,

我们的策略是，在大苏尔的户外

and we watch the sunset in radio frequencies,

通过无线电频率观看日落，

and we try and detect the reflection of the sun off the surface of the ocean.

并尝试着探测太阳在 海平面落下的反射。

Now, I know you're thinking, "There are no glaciers at Big Sur."

现在，我知道你们在想 “大苏尔没有冰川啊！”

(Laughter)

（观众笑声）

And that's true.

没错。

(Laughter)

（观众笑声）

But it turns out that detecting the reflection of the sun

但我们后来发现探测太阳

在海洋平面落下时的反射，

off the surface of the ocean

与探测一块冰层底部的反射

and detecting the reflection off the bottom of an ice sheet

are extremely geophysically similar.

在地理学上极度地相似。

And if this works,

如果这个方法奏效的话，

we should be able to apply the same measurement principle in Antarctica.

我们应该能够在南极 运用同样的测量原理。

而且这个想法并不是 看起来的那样遥不可及。

And this is not as far-fetched as it seems.

地震行业经历了一个 相似的技术上的发展，

The seismic industry has gone through a similar technique-development exercise,

使他们能够从以引爆炸药 作为一种来源，

where they were able to move from detonating dynamite as a source,

过渡到利用周围环境的地震噪音。

to using ambient seismic noise in the environment.

And defense radars use TV signals and radio signals all the time,

防御性雷达在一直以来都使用 电视信号以及无线电信号，

so they don't have to transmit a signal of radar

所以它们不用发送雷达信号

and give away their position.

来标记它们的位置。

So what I'm saying is, this might really work.

我的意思是， 这也许真的是个好办法。

And if it does, we're going to need extremely low-cost sensors

如果事实如此，我们将会 需要极低成本的传感器，

so we can deploy networks of hundreds or thousands of these on an ice sheet

然后可以在冰层上调配上百个 以致上千个这样的传感器

to do imaging.

去做成像。

And that's where the technological stars have really aligned to help us.

那正是科技开始真正联合起来 帮助我们的开始。

Those earlier radar systems I talked about

这些我所提及的早期的雷达系统

were developed by experienced engineers over the course of years

是有经验的工程师利用国有设施 及昂贵的专业设备

at national facilities

经历了数年

才逐渐发展起来的。

with expensive specialized equipment.

But the recent developments in software-defined radio,

但最近在软件无线电的发展中，

rapid fabrication and the maker movement,

快速制造和制造运动

make it so that it's possible for a team of teenagers

使得那些在我的实验室

working in my lab over the course of a handful of months

工作了数月的青少年 建立一个雷达原型

to build a prototype radar.

成为了可能。

OK, they're not any teenagers, they’re Stanford undergrads,

好吧，他们并不是普通的青少年， 而是斯坦福的大学生，

but the point holds --

但是我想说的是——

(Laughter)

（观众笑声）

that these enabling technologies are letting us break down the barrier

这些技术使我们能够冲破

between engineers who build instruments and scientists that use them.

建立仪器的工程师 和使用它们的科学家之间的障碍。

And by teaching engineering students to think like earth scientists

通过教授工程专业的学生 去像地球科学家一样思考，

and earth-science students who can think like engineers,

以及可以像工程师一样思考的 地球科学系的学生，

我的实验室正在建立一个 可以为每一个现存的问题

my lab is building an environment in which we can build custom radar sensors

for each problem at hand,

定制雷达传感器的环境，

that are optimized for low cost and high performance

这些传感器会针对不同的问题进行

for that problem.

低成本和高性能的优化。

And that's going to totally change the way we observe ice sheets.

那将完全改变 我们观察冰层的方式。

Look, the sea level problem and the role of the cryosphere in sea level rise

总之，海平面问题和冰雪圈 在海平面上升问题中

扮演着极其重要的角色，

is extremely important

and will affect the entire world.

而且会影响到整个世界。

But that is not why I work on it.

但还那不是我致力于 这项研究的原因。

I work on it for the opportunity to teach and mentor

我致力于教授和引导

extremely brilliant students,

极其聪慧的学生，

because I deeply believe that teams of hypertalented,

因为我深信由智慧过人，

hyperdriven, hyperpassionate young people

充满能量和极其富有热情的 年轻人组成的团队

can solve most of the challenges facing the world,

可以解决世界所面对的 大部分挑战，

and that providing the observations required to estimate sea level rise

而刚刚讲到的为预测 海平面上升所提供的观测技术，

is just one of the many such problems they can and will solve.

只是他们可以解决的 许多问题中的一个。

Thank you.

谢谢大家。

(Applause)

（观众掌声）