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

譯者: Lilian Chiu 審譯者: Helen Chang

When was I was 21 years old,

當我二十一歲時，

I had all this physics homework.

我有一堆物理的作業。

Physics homework requires taking breaks,

寫物理作業需要休息，

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

維基百科當時相對很新， 所以我常在那裡休息。

I kept going back to the same articles,

我不斷回去看同樣的文章，

reading them again and again,

一而再再而三地閱讀，

on glaciers, Antarctica and Greenland.

多半是關於冰河、南極洲、 格林蘭島的文章。

How cool would it be to visit these places

如果能造訪這些地方，會有多酷？

and what would it take to do so?

要什麼代價才能這麼做？

Well, here we are

我們這裡看到的，

on a repurposed Air Force cargo plane

是由美國太空總署 重新改裝的空軍運輸機

operated by NASA

flying over the Greenland ice sheet.

飛過格林蘭的大冰原時 看出去的畫面。

There's a lot to see here,

這裡有很多值得看的，

but there's more that is hidden,

但還有更多是隱藏的、

waiting to be uncovered.

尚待發掘的。

What the Wikipedia articles didn't tell me

維基百科的文章沒有告訴我

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

有液態的水隱藏在大冰原的內部，

because we didn't know that yet.

因為我們還不知道這一點。

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

不過我的確有從維基百科 學到格林蘭很大，

the size of Mexico,

和墨西哥一樣大，

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

冰的厚度，從頂部到底部共兩英哩。

But it's not just static.

但它不是靜態的。

The ice flows like a river downhill towards the ocean.

冰就像河流一樣， 會流下山，流入海洋。

As it flows around bends,

當它流過彎道，

it deforms and cracks.

它會變形、破裂。

I get to study these amazing ice dynamics,

我得以研究這些驚人的冰動態，

which are located in one of the most remote physical environments

它們的所在地， 是地球上現存最偏遠的

remaining on earth.

物理環境之一。

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

現在投入研究冰河學，就像是來到

at Facebook in the 2000s.

21 世紀初臉書的開端。

(Laughter)

（笑聲）

Our capability to fly airplanes and satellites over the ice sheets

我們能讓飛機和衛星 飛過大冰原上方的能力，

is revolutionizing glaciology.

對冰河學來說是項革新。

It's just starting to do for science

它開始對科學產生的作用，

what the smartphone has done for social media.

就像智慧手機 對社交媒體產生的作用。

The satellites are reporting a wealth of observations

衛星能回報許多觀察資料，

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

不斷揭露出許多 關於大冰原的隱藏事實。

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

比如，我們有格林蘭大冰原 大小的觀察資料，

every month going back to 2002.

從 2002 年開始每個月都有記錄。

You can look towards the bottom of the screen here

各位可以看一下螢幕的底端，

to see the month and the year go forward.

有相對應的月份和年份。

You can see that some areas of the ice sheet melt

可以看到大冰原的一些區域會融化

or lose ice in the summer.

或是在夏天時失去冰。

Other areas experience snowfall

其他區域則會遇到下雪

or gain ice back in the winter.

或是在冬天時重新生成冰。

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

不過，這種季節性循環， 與總量損失的速度一比就相形失色，

that would have stunned a glaciologist 50 years ago.

五十年前的冰河學家 對此一定會很驚訝。

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

我們從來不會料到，大冰原失量 而流入海洋的速度會這麼快。

Since these measurements began in 2002,

從 2002 年開始記錄這些測量值起，

the ice sheet has lost so much ice

大冰原已經損失了大量的冰，

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

如果把它轉變成的水 堆積在我們最小的大陸上，

it would drown Australia knee-deep.

澳洲的水就會淹到膝蓋這麼深了。

How is this possible?

這怎麼可能？

Well, under the ice lies the bedrock.

在冰底下的是基岩。

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

針對冰所流經的 山丘、山谷、山岳、窪地，

that the ice flows over.

我們用雷達來製作出影像。

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

藏在大冰原底下的 是大峽谷這麼大的水道，

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

將來自格林蘭的冰和水導入海中。

The reason that radar can reveal the bedrock

雷達能夠看到基岩的原因，

is that ice is entirely transparent to radar.

是因為對雷達而言， 冰是完全透明的。

You can do an experiment.

你們可以做個實驗。

Go home and put an ice cube in the microwave.

回家，把一個冰塊放到微波爐中。

It won't melt,

它不會融化，

because microwaves, or radar,

因為微波，或雷達，

pass straight through the ice without interacting.

會直接穿透冰，不會有相互作用。

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

若你想要將冰塊融解， 你得把它弄濕，

because water heats up easily in the microwave.

因為在微波之下， 水很容易就會加溫。

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

那就是設計微波爐的原理。

Radar can see water.

雷達能看得見水。

And radar has revealed a vast pool of liquid water

雷達顯示出一個巨大的液態水水池，

hidden under my colleague Olivia,

它就隱藏在我同事奧莉微雅

seven stories beneath her feet.

腳下七層樓的位置。

Here, she's used a pump

照片中，她在用幫浦

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

把一些水抽回到大冰原的表面上。

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

六年前，我們甚至不知道 有這個冰河含水層存在。

The aquifer formed

含水層形成的原因，

when snow melts in the summer sun

是夏天太陽照射導致融雪，

and trickles downward.

融雪再向下流。

It puddles up in huge pools.

它積成大池子。

From there, the snow acts as an igloo,

在那裡，雪的作用就像圓頂冰屋，

insulating this water from the cold and the wind above.

把這地下水和上面的 嚴寒和寒風隔離開。

So the water can stay hidden in the ice sheet

因此，水可以繼續 以液態的形式隱藏在

in liquid form year after year.

大冰原之下，一年又一年繼續下去。

The question is, what happens next?

問題是，接下會發生什麼事？

Does the water stay there forever?

水就會永遠留在那裡嗎？

It could.

有可能。

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

或是水會找到出路， 進入到全球海洋中？

One possible way for the water to reach the bedrock

水要到達基岩，再從那裡到達海洋，

and from there the ocean

其中的途徑之一，

is a crevasse, or a crack in the ice.

就是冰隙，或是冰的裂縫。

When cracks fill with water,

當裂縫充滿了水，

the weight of the water forces them deeper and deeper.

水的重量會迫使裂縫不斷加深。

This is how fracking works

這就是壓裂法

to extract natural gas from deep within the earth.

從地球深處取得天然瓦斯的方式。

Pressurized fluids fracture rocks.

加壓的液體會使岩石破裂。

All it takes is a crack to get started.

只要有一處裂縫做為起頭即可。

Well, we recently discovered

我們最近發現，

that there are cracks available in the Greenland ice sheet

在格林蘭大冰原上的確有裂縫，

near this glacier aquifer.

距離這個冰河含水層很近。

You can fly over most of the Greenland ice sheet

你飛過格林蘭大冰原上的大部份地方

and see nothing,

可能什麼都看不到，

no cracks, no features on the surface,

沒有裂縫、沒有地表特徵，

but as this helicopter flies towards the coast,

但當這架直升機飛向海岸，

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

水要流下山丘時可能會走的路徑，

one crack appears,

有一個裂縫出現了，

then another and another.

接著又一個，又再一個。

Are these cracks filled with liquid water?

這些裂縫有充滿了水嗎？

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

如果有，它們把水帶到多深的地方？

Can they take it to the bedrock

它們能把水帶到基岩

and the ocean?

以及海洋嗎？

To answer these questions,

若要回答這些問題，

we need something beyond remote sensing data.

光是遙感探測資料是不夠的。

We need numeric models.

我們需要數值模型。

I write numeric models that run on supercomputers.

我寫在超級電腦上執行的數值模型。

A numeric model is simply a set of equations

數值模型就是一組方程式，

that works together to describe something.

這些方程式結合起來可描述某事物。

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

可能很簡單，只是 序列的下一個數字──

one, three, five, seven --

1、3、5、7 ──

or it can be a more complex set of equations

也可能是一組比較複雜的方程式，

that predict the future

根據現在已知條件

based on known conditions in the present.

來預測未來。

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

而我們的情況是需要找到 描述冰如何破裂的方程式。

Well, engineers already have a very good understanding

工程師已經非常了解

of how aluminum, steel and plastics fracture under stress.

在壓力之下，鋁、鋼、 塑膠會如何斷裂。

It's an important problem in our society.

那是我們社會中的一個重要問題。

And it turns out that the engineering equations

結果發現，工程上用來說明材料

for how materials fracture

如何斷裂的方程式，

are not that different from my physics homework.

和我的物理作業沒有很大的不同。

So I borrowed them, adapted them for ice,

所以我借用了它們，針對冰做改寫，

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

我就得到了一個數值模型， 可以說明當冰隙充滿了

來自含水層的水時，它會如何破裂。

when filled with water from the aquifer.

This is the power of math.

這就是數學的力量。

It can help us understand real processes in our world.

它能協助我們了解 我們世界上的實際情況。

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

現在來看看，我的數值模型 產出了什麼結果，

but first I should point out

但，首先，我要說明一點，

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

冰隙的深度和寬度差了千倍，

so in the main panel here,

所以在這面大螢幕上，

we've zoomed in to better see the details.

我們會放大來看清楚細節。

You can look to the smaller panel on the right

你們可以看看右邊比較小的螢幕，

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

那裡呈現的是冰隙的 真實比例，又高又瘦。

As the aquifer water flows into the crevasse,

隨著含水層的水流入裂隙，

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

在攝氏零下 15 度的冰中， 有部份的水會結冰。

That's about as cold as your kitchen freezer.

那溫度和你廚房裡的 冰箱溫度一樣低。

But this loss can be overcome

但這種水損失是可以被克服的，

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

如果冰河含水層的水 流速夠高就可以。

In our case, it is,

我們遇到的情況就是如此，

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

含水層的水延著冰隙 一路通到一千公尺以下的

a thousand meters below.

大冰原基部。

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

從那裡就有條順暢的路徑 可以直達海洋。

So the aquifer water is a part

所以，全球社會所經歷到

of the three millimeters per year of sea level rise

海平面每年上升三毫米的現象，

that we experience as a global society.

部份原因就是含水層的水。

But there's more:

但還不只這樣：

the aquifer water might be punching above its weight.

含水層的水可能 還會做超乎預期的事。

The ice flows in complex ways.

冰的流動方式很複雜。

In some places, the ice flows very fast.

在一些地方，冰的流動非常快。

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

在這些地方，大冰原的 基部通常就會有水。

In other places, not so fast.

在其他地方流速就沒那麼快。

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

那些地方通常就沒有水。

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

現在我們已經知道含水層的水 會到達大冰原的基部了，

the next question is:

下一個問題就是：

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

它是否會讓冰本身 流向海洋的速度更快？

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

我們在試著解開這些隱藏在 格林蘭大冰原內的謎題，

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

這樣我們才能做更好的規劃， 因應它造成的海平面上升。

The amount of ice that Greenland has lost since 2002

從 2002 年開始， 格林蘭所喪失的冰量，

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

相對於大冰原含有的冰量， 是非常微小的。

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

大冰原是巨大且強大的機器， 在很長的時間尺度上運作。

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

在接下來八十年，全球海平面 會再上升至少 20 公分，

perhaps as much as one meter,

甚至有可能到 1 公尺，

and maybe more.

也許更高。

Our understanding of future sea level rise is good,

我們對於未來海平面 上升的情況算是很了解，

but our projections have a wide range.

但我們預測值的範圍很大。

It's our role as glaciologists and scientists

我們身為冰河學家和科學家的職責，

to narrow these uncertainties.

就是要降低這些不確定性。

How much sea level rise is coming,

將來海平面還會上升多少、

and how fast will it get here?

上升的速度又有多快？

We need to know how much and how fast,

我們需要知道上升多少、上升多快，

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

讓世界和其社區能夠針對將來的 海平面上升做出因應計畫。

Thank you.

謝謝。

(Applause)

（掌聲）