When was I was 21 years old, I had all this physics homework.
我21岁的时候，有很多物理作业。
Physics homework requires taking breaks, and Wikipedia was relatively new, so I took a lot of breaks there.
做物理作业的时候需要休息，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, reading them again and again, on glaciers, Antarctica and Greenland.
我总是看同一篇文章，反反复复地看，关于冰川、南极洲和格陵兰岛的。
How cool would it be to visit these places and what would it take to do so?
如果能去那些地方该有多酷啊，需要做什么准备呢？
Well, here we are on a repurposed Air Force cargo plane operated by NASA flying over the Greenland ice sheet.
让我们来看看，在一辆被改造的空军客机上，客机由NASA操作，从格陵兰岛的冰原上方飞过。
There's a lot to see here, but there's more that is hidden, waiting to be uncovered.
你可以看到很多东西，但是更多的是看不到的，等待被发掘。
What the Wikipedia articles didn't tell me is that there's liquid water hidden inside the ice sheet,
维基百科没有告诉我的是，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, the size of Mexico,
维基百科只告诉我，格陵兰岛的冰原面积极大，和墨西哥的大小差不多，
and its ice from top to bottom is two miles thick. But it's not just static.
它的整个冰层足有2英里厚。但它并非静止不动。
The ice flows like a river downhill towards the ocean. As it flows around bends, it deforms and cracks.
冰块就像河水一样沿着山体流向海中。当它流经弯道的时候，冰块会变形然后破裂。
I get to study these amazing ice dynamics, which are located in one of the most remote physical environments remaining on earth.
我开始接触到这种惊人的冰学动态，它位于地球上现存的最荒僻的自然环境中。
To work in glaciology right now is like getting in on the ground floor at Facebook in the 2000s.
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。
Our capability to fly airplanes and satellites over the ice sheets is revolutionizing glaciology.
我们在冰原上方驾驶飞机以及已有卫星的能力，正引发着冰川学的变革。
It's just starting to do for science what the smartphone has done for social media.
它对于科学的作用，就像智能手机对于社交媒体一样重要。
The satellites are reporting a wealth of observations that are revealing new hidden facts about the ice sheets continuously.
卫星报告的大量观测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 every month going back to 2002.
例如，我们有格陵兰岛冰原大小的观测数据，从2002年至今的每个月都有。
You can look towards the bottom of the screen here to see the month and the year go forward.
你们可以看到屏幕的下方，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 or lose ice in the summer.
你们可以看到在某些区域冰原融化，或是在夏天的时候彻底消融。
Other areas experience snowfall or gain ice back in the winter.
其他的区域经历着降雪，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 that would have stunned a glaciologist 50 years ago.
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。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 that if that water were piled up on our smallest continent, it would drown Australia knee-deep.
冰原已经有大量的冰流失，如果那些融化的水积聚在澳大利亚这块世界上最小的大陆上，将会有膝盖那么深。
How is this possible? Well, under the ice lies the bedrock.
这怎么可能呢？事实上，在冰的下面是基岩。
We used radar to image the hills, valleys, mountains and depressions that the ice flows over.
我们用雷达描绘山丘、峡谷、山脉和洼地的图像，那些冰块川流过的地方。
Hidden under the ice sheet are channels the size of the Grand Canyon that funnel ice and water off of Greenland and into the ocean.
在冰原下是和美国大峡谷一般大的海峡，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 is that ice is entirely transparent to radar.
雷达可以展现基岩的原因在于对于雷达而言，冰是完全透明的。
You can do an experiment. Go home and put an ice cube in the microwave.
你们可以做一个实验。回家把冰块放在微波炉中。
It won't melt, because microwaves, or radar, pass straight through the ice without interacting.
它不会融化，因为微波或者雷达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, because water heats up easily in the microwave.
如果你想使冰块融化，应该先把它变湿，因为水在微波中容易升温。
That's the whole principle the microwave oven is designed around. Radar can see water.
那是微波炉的设计原理，雷达看得见水。
And radar has revealed a vast pool of liquid water hidden under my colleague Olivia, seven stories beneath her feet.
雷达显示了极大量的液态水隐藏在我同事Olivia的脚下，大概有七层楼高。
Here, she's used a pump to bring some of that water back to the ice sheet's surface.
她正在用一个泵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 when snow melts in the summer sun and trickles downward. It puddles up in huge pools.
含水层形成于雪在夏日下融化，然后慢慢地向下流。它在巨大的水坑中搅动。
From there, the snow acts as an igloo, insulating this water from the cold and the wind above.
从那儿开始，雪就像冰屋一样，将水与上方的寒冷和风隔绝开。
So the water can stay hidden in the ice sheet in liquid form year after year.
所以水得以隐藏在冰原之下，以液态年复一年地存在着。
The question is, what happens next? Does the water stay there forever? It could.
问题是，接下来会发生什么呢？那些水会永远待在那儿吗？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 and from there the ocean is a crevasse, or a crack in the ice.
水要流到基岩并且从那儿流入海洋的一种可行方法，是找到一个决口，或是冰里面的缝隙。
When cracks fill with water, the weight of the water forces them deeper and deeper.
当裂缝中充满了水，水的重量使它们不断向下开裂。
This is how fracking works to extract natural gas from deep within the earth.
这是液态破碎法的工作原理，使地球深处的天然气流出。
Pressurized fluids fracture rocks. All it takes is a crack to get started.
增压的流体使岩石破碎。这一切只需要从一个裂缝开始。
Well, we recently discovered that there are cracks available in the Greenland ice sheet near this glacier aquifer.
我们最近发现，在格陵兰岛的冰原就有这样的裂缝，在冰川含水层附近。

You can fly over most of the Greenland ice sheet and see nothing, no cracks, no features on the surface,
你可以飞过格陵兰岛的大部分冰原，但你什么都看不到，没有裂缝，表面也没有任何征兆，
but as this helicopter flies towards the coast, the path that water would take on its quest to flow downhill,
但是当这架直升机飞向海岸，沿着水流下山的路径，
one crack appears, then another and another.
一个裂缝出现了，接着一个又一个。
Are these cracks filled with liquid water? And if so, how deep do they take that water?
这些裂缝中都充满了液态水吗？如果是的话，那些水有多深呢？
Can they take it to the bedrock and the ocean?
它们深到基岩了吗，或者是海洋？
To answer these questions, we need something beyond remote sensing data. We need numeric models.
为了回答这些问题，我们需要一些遥感数据以外的信息。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 that works together to describe something.
一个数学模型只是一组方程式，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 -- one, three, five, seven
它可能和序列中下一个数字一样简单--1，3，5，7，
or it can be a more complex set of equations that predict the future based on known conditions in the present.
或者也可以是更复杂的方程组，基于现在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 of how aluminum, steel and plastics fracture under stress.
工程师已经熟知关于铝、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 for how materials fracture are not that different from my physics homework.
事实证明，工程师关于材料如何断裂的数模方程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 when filled with water from the aquifer.
于是我建立了一个关于当裂缝充满了来自含水层的水会如何断裂的数学模型。
This is the power of math. It can help us understand real processes in our world.
这是数学的力量。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 that the crevasse is about a thousand times narrower than it is deep,
但是首先我要指出，这些决口的宽度比它们的深度小1000倍，
so in the main panel here, we've zoomed in to better see the details.
所以在这个主面板上，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 to see the true scale for how tall and skinny the crevasse is.
你们可以参考右边那个更小的数据条来估算这些狭长裂缝的真实尺寸比例。
As the aquifer water flows into the crevasse, some of it refreezes in the negative 15 degree Celsius ice.
因为含水层的水流入了裂缝，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 if the flow rate in from the glacier aquifer is high enough.
但是如果来自含水层的流量足够大的话，这部分的缺失是可以克服的。
In our case, it is, and the aquifer water drives the crevasse all the way to the base of the ice sheet a thousand meters below.
在我们的案例中，情况就是这样的，含水层的水使裂缝裂到冰原的底部，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 of the three millimeters per year of sea level rise that we experience as a global society.
所以含水层的水对每年海平面3毫米的上升有部分的影响，这正是我们全球社会所经历的。
But there's more: the aquifer water might be punching above its weight. The ice flows in complex ways.
但是还有别的问题：含水层的流量可能不足。冰以复杂的方式流动。
In some places, the ice flows very fast. There tends to be water at the base of the ice sheet here.
在有的地方冰流动很快。它们可能在冰原的底部变成水。
In other places, not so fast. Usually, there's not water present at the base there.
在其他地方则没有这么快。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, the next question is:
既然我们知道了含水层的水会到达冰原底部，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 is just a small fraction of what that ice sheet holds.
从2002年起，格陵兰岛流失的冰量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, perhaps as much as one meter, and maybe more.
在未来的80年，全球海平面至少会上升20厘米，甚至可能是1米，也有可能更多。
Our understanding of future sea level rise is good, but our projections have a wide range.
我们对于未来海平面的了解是好的，但是我们的预测太宽泛了。
It's our role as glaciologists and scientists to narrow these uncertainties.
我们作为冰川学家和科学家的责任就是减少这些不确定性。
How much sea level rise is coming, and how fast will it get here?
海平面会上涨多少，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. Thank you.
这样社会各界才能做好准备，应对未来的海平面上升。谢谢。