What's hidden under the Greenland ice sheet? | Kristin Poinar

翻译人员: 校对人员: Yolanda Zhang

When was I was 21 years old,

我21岁的时候

有很多物理作业

I had all this physics homework.

Physics homework requires taking breaks,

做物理作业的时候需要休息

and Wikipedia was relatively new, so I took a lot of breaks there.

当时维基百科刚刚兴起 所以我经常在那儿浏览 放松

I kept going back to the same articles,

我总是看同一篇文章

reading them again and again,

反反复复地看

on glaciers, Antarctica and Greenland.

关于冰川 南极洲和格陵兰岛的

How cool would it be to visit these places

如果能去那些地方该有多酷啊

and what would it take to do so?

需要做什么准备呢

Well, here we are

让我们来看看

on a repurposed Air Force cargo plane

在一辆被改造的空军客机上

operated by NASA

客机由NASA操作

flying over the Greenland ice sheet.

从格陵兰岛的冰原上方飞过

There's a lot to see here,

你可以看到很多东西

but there's more that is hidden,

但是更多的是看不到的

waiting to be uncovered.

等待被发掘

What the Wikipedia articles didn't tell me

维基百科没有告诉我的是

is that there's liquid water hidden inside the ice sheet,

在冰原下面有隐藏的液态水

because we didn't know that yet.

因为当时没有人知道

I did learn on Wikipedia that the Greenland ice sheet is huge,

维基百科只告诉我 格陵兰岛的冰原面积极大

the size of Mexico,

和墨西哥的大小差不多

and its ice from top to bottom is two miles thick.

它的整个冰层足有2英里厚

But it's not just static.

但它并非静止不动

The ice flows like a river downhill towards the ocean.

冰块就像河水一样沿着山体流向海中

As it flows around bends,

当它流经弯道的时候

it deforms and cracks.

冰块会变形然后破裂

I get to study these amazing ice dynamics,

我开始接触到这种惊人的冰学动态，

which are located in one of the most remote physical environments

它位于地球上现存的最荒僻的

remaining on earth.

自然环境中

To work in glaciology right now is like getting in on the ground floor

要立刻投入冰川学的工作

就像在20世纪末抢先创建 脸书 一样

at Facebook in the 2000s.

(Laughter)

（笑）

Our capability to fly airplanes and satellites over the ice sheets

我们在冰原上方驾驶飞机 以及已有卫星的能力

is revolutionizing glaciology.

正引发着冰川学的变革

It's just starting to do for science

它对于科学的作用

what the smartphone has done for social media.

就像智能手机对于社交媒体一样重要

The satellites are reporting a wealth of observations

卫星报告的大量观测

that are revealing new hidden facts about the ice sheets continuously.

都持续地发掘着冰原下的秘密

For instance, we have observations of the size of the Greenland ice sheet

例如 我们有格陵兰岛冰原 大小的观测数据

every month going back to 2002.

从2002年至今的每个月都有

You can look towards the bottom of the screen here

你们可以看到屏幕的下方

to see the month and the year go forward.

观察随着年月的增加带来的数据变化

You can see that some areas of the ice sheet melt

你们可以看到在某些区域冰原融化

or lose ice in the summer.

或是在夏天的时候彻底消融

Other areas experience snowfall

其他的区域经历着降雪

or gain ice back in the winter.

或是在冬天的时候重新结冰

This seasonal cycle, though, is eclipsed by an overall rate of mass loss

然而这种季节周期性的变化 与总体质量的流失相比不值一提

that would have stunned a glaciologist 50 years ago.

这会使50年前的冰川学家目瞪口呆

We never thought that an ice sheet could lose mass into the ocean this quickly.

我们从未想过 冰原流失的速度会如此之快

Since these measurements began in 2002,

因为这些测量从2002年开始

the ice sheet has lost so much ice

冰原已经有大量的冰流失

that if that water were piled up on our smallest continent,

如果那些融化的水积聚在澳大利亚这 这块世界上最小的大陆上

it would drown Australia knee-deep.

将会有膝盖那么深

How is this possible?

这怎么可能呢

Well, under the ice lies the bedrock.

事实上 在冰的下面是基岩

We used radar to image the hills, valleys, mountains and depressions

我们用雷达描绘山丘 峡谷 山脉和洼地的图像

that the ice flows over.

那些冰块川流过的地方

Hidden under the ice sheet are channels the size of the Grand Canyon

在冰原下是和美国大峡谷 一般大的海峡

that funnel ice and water off of Greenland and into the ocean.

成漏斗形 将格陵兰岛上的 冰和水导入海洋中

The reason that radar can reveal the bedrock

雷达可以展现基岩的原因

is that ice is entirely transparent to radar.

在于对于雷达而言 冰是完全透明的

You can do an experiment.

你们可以做一个实验

Go home and put an ice cube in the microwave.

回家把冰块放在微波炉中

It won't melt,

它不会融化

because microwaves, or radar,

因为微波或者雷达

pass straight through the ice without interacting.

直接穿过冰块而不会对其发生作用

If you want to melt your ice cube, you have to get it wet,

如果你想使冰块融化 应该先把它变湿

because water heats up easily in the microwave.

因为水在微波中容易升温

That's the whole principle the microwave oven is designed around.

那是微波炉的设计原理

Radar can see water.

雷达看得见水

And radar has revealed a vast pool of liquid water

雷达显示了极大量的液态水

hidden under my colleague Olivia,

隐藏在我同事Olivia的脚下

seven stories beneath her feet.

大概有七层楼高

Here, she's used a pump

她正在用一个泵

to bring some of that water back to the ice sheet's surface.

将部分这些水运回冰原的表面

Just six years ago, we had no idea this glacier aquifer existed.

六年前 我们并不知道 这个冰川下方含水层的存在

The aquifer formed

含水层形成于

when snow melts in the summer sun

雪在夏日下融化

and trickles downward.

然后慢慢地向下流

It puddles up in huge pools.

它在巨大的水坑中搅动

From there, the snow acts as an igloo,

从那儿开始 雪就像冰屋一样

insulating this water from the cold and the wind above.

将水与上方的寒冷和风隔绝开

So the water can stay hidden in the ice sheet

所以水得以隐藏在冰原之下

in liquid form year after year.

以液态年复一年地存在着

The question is, what happens next?

问题是 接下来会发生什么呢

Does the water stay there forever?

那些水会永远待在那儿吗

It could.

这是可能的

Or does it find a way out to reach the global ocean?

或者它能找到一种 流入全球海洋的方法吗

One possible way for the water to reach the bedrock

水要流到基岩并且 从那儿流入海洋的

and from there the ocean

一种可行方法

is a crevasse, or a crack in the ice.

是找到一个决口 或是冰里面的缝隙

When cracks fill with water,

当裂缝中充满了水

the weight of the water forces them deeper and deeper.

水的重量使它们不断向下开裂

This is how fracking works

这是液态破碎法的工作原理

to extract natural gas from deep within the earth.

使地球深处的天然气流出

Pressurized fluids fracture rocks.

增压的流体使岩石破碎

All it takes is a crack to get started.

这一切只需要从一个裂缝开始

Well, we recently discovered

我们最近发现

that there are cracks available in the Greenland ice sheet

在格陵兰岛的冰原就有这样的裂缝

near this glacier aquifer.

在冰川含水层附近

You can fly over most of the Greenland ice sheet

你可以飞过格陵兰岛的大部分冰原

and see nothing,

但你什么都看不到

no cracks, no features on the surface,

没有裂缝 表面也没有任何征兆

but as this helicopter flies towards the coast,

但是当这架直升机飞向海岸

the path that water would take on its quest to flow downhill,

沿着水流下山的路径

one crack appears,

一个裂缝出现了

then another and another.

接着一个又一个

Are these cracks filled with liquid water?

这些裂缝中都充满了液态水吗

And if so, how deep do they take that water?

如果是的话 那些水有多深呢

Can they take it to the bedrock

它们深到基岩了吗

and the ocean?

或者是海洋

To answer these questions,

为了回答这些问题

we need something beyond remote sensing data.

我们需要一些遥感数据以外的信息

We need numeric models.

我们需要数学模型

I write numeric models that run on supercomputers.

我编写了一个在超型计算机上 运行的数学模型

A numeric model is simply a set of equations

一个数学模型只是一组方程式

that works together to describe something.

它们一起运作时可以描述一些东西

It can be as simple as the next number in a sequence --

它可能和序列中下一个数字一样简单

one, three, five, seven --

1 3 5 7

or it can be a more complex set of equations

或者也可以是更复杂的方程组

that predict the future

基于现在

based on known conditions in the present.

已知的条件预测未来

In our case, what are the equations for how ice cracks?

在我们的案例中描述 冰裂的方程式是什么呢

Well, engineers already have a very good understanding

工程师已经熟知

of how aluminum, steel and plastics fracture under stress.

关于铝 钢和塑料在压力下如何断裂

It's an important problem in our society.

这对于我们的社会生活十分重要

And it turns out that the engineering equations

事实证明 工程师关于材料如何断裂的

for how materials fracture

数模方程

are not that different from my physics homework.

和我的物理作业没有什么不同

So I borrowed them, adapted them for ice,

所以我借鉴了它们 并运用到冰中

and then I had a numeric model for how a crevasse can fracture

于是我建立了一个关于 当裂缝充满了来自含水层的水

when filled with water from the aquifer.

会如何断裂的数学模型

This is the power of math.

这是数学的力量

It can help us understand real processes in our world.

它能帮我们了解这个世界中 一个个真实的过程

I'll show you now the results of my numeric model,

我现在要向你们展示 我的数模计算结果

but first I should point out

但是首先我要指出

that the crevasse is about a thousand times narrower than it is deep,

这些决口的宽度 比它们的深度小1000倍

so in the main panel here,

所以在这个主面板上

we've zoomed in to better see the details.

我们放大了它以便更好地观察细节

You can look to the smaller panel on the right

你们可以参考右边那个更小的数据条

to see the true scale for how tall and skinny the crevasse is.

来估算这些狭长裂缝的真实尺寸比例

As the aquifer water flows into the crevasse,

因为含水层的水流入了裂缝

some of it refreezes in the negative 15 degree Celsius ice.

其中一部分在零下15摄氏度结冰了

That's about as cold as your kitchen freezer.

和厨房冰箱的冷冻层一样冷

But this loss can be overcome

但是这部分的缺失是可以克服的

if the flow rate in from the glacier aquifer is high enough.

如果来自含水层的流量足够大的话

In our case, it is,

在我们的案例中情况就是这样的

and the aquifer water drives the crevasse all the way to the base of the ice sheet

含水层的水使裂缝裂到冰原的底部

a thousand meters below.

海拔 负1000米

From there, it has a clear path to reach the ocean.

在那儿 有一条很清晰的 通往海洋的路径

So the aquifer water is a part

所以含水层的水部分影响了

of the three millimeters per year of sea level rise

每年海平面3毫米的上升

that we experience as a global society.

这正是我们全球社会所经历的

But there's more:

但是还有别的问题

the aquifer water might be punching above its weight.

含水层的流量可能不足

The ice flows in complex ways.

冰以复杂的方式流动

In some places, the ice flows very fast.

在有的地方冰流动很快

There tends to be water at the base of the ice sheet here.

它们可能在冰原的底部变成水

In other places, not so fast.

在其他地方则没有这么快

Usually, there's not water present at the base there.

通常情况下在底部没有水的出现

Now that we know the aquifer water is getting to the base of the ice sheet,

既然我们知道了 含水层的水会到达冰原底部

the next question is:

那么下一个问题是

Is it making the ice itself flow faster into the ocean?

它会加快冰流入海洋的速度吗

We're trying to uncover these mysteries hidden inside the Greenland ice sheet

我们尝试着去解开 藏在格陵兰岛冰原下的秘密

so that we can better plan for the sea level rise it holds.

以便更好地规划解决 它所造成的海平面上升问题

The amount of ice that Greenland has lost since 2002

从2002年起格陵兰岛流失的冰量

is just a small fraction of what that ice sheet holds.

只是那片冰原体积的一小部分

Ice sheets are immense, powerful machines that operate on long timescales.

冰原是巨型 强大 可以长时间工作的调节器

In the next 80 years, global sea levels will rise at least 20 centimeters,

在未来的80年 全球海平面至少会上升20cm

perhaps as much as one meter,

甚至可能是1米

and maybe more.

也有可能更多

Our understanding of future sea level rise is good,

我们对于未来海平面的了解是好的

but our projections have a wide range.

但是我们的预测太宽泛了

It's our role as glaciologists and scientists

我们作为冰川学家和 科学家的责任就是

to narrow these uncertainties.

减少这些不确定性

How much sea level rise is coming,

海平面会上涨多少

and how fast will it get here?

上涨多快

We need to know how much and how fast,

我们需要知道它的变化幅度和速度

so the world and its communities can plan for the sea level rise that's coming.

这样社会各界才能做好准备 应对未来的海平面上升

Thank you.

谢谢

(Applause)

（掌声）