英国皇家科学院圣诞讲座2020行星地球（2020）

我们可以开始看看它们重要在哪里
we can start to see why they matter.
它们的其中一个功绩
And one of the things they do
就是创造了世界上最大的瀑布
is to create the largest waterfall in the world.
我们到地球仪这边来
So, let's come over to the map over here.
我们要去地球上一个非常独特的地方
We're going to go to a very specific place on the globe.
我们看看这里
We're going to look up here.
我们回去 在这里我们可以看到格陵兰岛
Let's come back, and here we can see Greenland.
这是北大西洋 这里是冰岛
This is the North Atlantic and we've got Iceland here.
这就是我们要看的那片区域
So, this region is where we're going to be looking.
但我想让你们看看在水下是什么样
But I want to show you what it really looks like underwater,
因为哪怕在巨大的风暴中
because even in a really big storm,
海面依然非常平静
the surface of the ocean is really quite flat.
但假如我们看看海面以下
But, if we look underneath the surface,
根本不是这样
it doesn't look like that at all.
我这里有个很棒的沙盒
I've got this fabulous sandbox here.
冰岛
格陵兰岛
为了帮你们定位
Now just to orient you,
我们来看地图上的那片区域
so we looked at that area on the map,
在沙盒中 这边是格陵兰岛
and in the sandbox Greenland is on this side,
而北大西洋一直往我的对面延伸
so the North Atlantic is stretching down that way away from me.
冰岛在这里 而我站的地方是北冰洋
Iceland is over here and I'm standing in the Arctic right now.
所以 这里都是海底
So, this is all sea floor.
这里的盆地非常深
This is a really deep basin down here,
大约两千米深
it's about two kilometres deep.
我走到另一边去
So, I'm going to walk around the other side
开始挖掘 因为这一边是大西洋
and start digging because on this side we've got the Atlantic,
所以这里需要大量的挖掘工作
so this is going to be quite a lot of digging.
这里的海洋非常深
So, the ocean here is really deep.
在海底之下还有
It's going to go down to about three or four kilometres
三到四千米
beneath the sea floor.
所以 这需要花点功夫
So, it's taking a bit of work here.
格陵兰岛在这个过程中变得更大一些了
Greenland's getting a bit bigger in the process.
冰岛在那里
Iceland's over there.
好了 我们现在可以看清形状了
OK, so we're starting to see the shape here now.
所以 这是北大西洋
So, we've got - this is the North Atlantic.
所以我们现在能看到 首先
So, what we can see now is, first of all,
海底是有形状的
that the sea floor has shape.
这就是海底的样子
There's all this stuff going on,
即使我们从海平面上看不出来
even though we can't see it from the surface.
海面之下有山脉 山谷和广阔的平原
There are mountains and valleys and vast plains underwater
而且它们非常巨大
and they are enormous.
就是我们看到的这样 有两个巨大的盆地
This is what we can see here, these two massive basins.
而且中间有一个山脊
And there's a ridge in between
从格陵兰岛延伸至冰岛
stretching from Greenland to Iceland.
我们来看一下这条线
So, we're going to look at a line,
穿过这一区域的横断面
a cross section, that goes through this bit here.
而我们有一个它的模型
And we've got a model of it over here.
这是横断面
So, here's our cross section.
这边是北冰洋
We've got the Arctic on this side
而这里是南边的大西洋
and this is the south where the Atlantic is.
首先我们可以看到
So, the first thing is that we can see
这里所有的海水
that all of this water in here,
看起来都一样 是吧 只是海水而已
it all looks the same, right? It's just water.
好 我加一点红色食用颜料进去
Well, I'm going to add a little bit of red food dye to it.
只加在上面
Just in the top here.
所以我们看到
So what we can see
红色食用颜料停留在水面
is that this red food dye is staying at the surface
而它停留在水面的原因是
and there's a reason that it's staying at the surface
这里实际有两层海水
because there are actually two layers of water in here.
只是我们之前看不出来
It's just that we couldn't see them before.
如果从这一边看
If we look at this from the side,
我们可以看到这里是暖水层
what we can see is that there's this warm layer,
一层温暖的海水
a layer of warm water in here.
而红色颜料让你能看到它在哪里
And the red dye has just showed you where it is.
但下面的海水更冷一点
But underneath the water is a little bit cooler.
而温度所起的作用
And the thing that the temperature is doing is
是改变海水的浮力
it's changing the buoyancy of the water,
所以红色的温暖海水停留在表层
so that red warm water stays at the top.
它不会和下面的海水混合
It doesn't mix with the water underneath.
而这就是海洋有结构的原因
And that's why the ocean has structure,
因为它不会全混合在一起
because it doesn't all just mix up.
现在 海伦将会从这里释放冷水
So, now, Helen here's going to release this cold water here.
这是北冰洋海水 非常冷
So, this is Arctic water that's really cold.
我们可以看看它会如何
And we're going to have a look at what it does.
它就这样 倾泻到底部
And there it goes, cascading down to the bottom.
这是冷的 高密度的海水
So, this is cold, dense water
而当它越过山脊
and it's flowing over the ridge
它会填满这里的盆地
and it's filling up the basin over here.
让我们再来看看这对我们的模型有什么影响
So, let's have a look at what this means back on our model here.
在这里 上面是格陵兰海
Here we are. This is the Greenland Sea up here.
这里是北冰洋海水
This is the cold Arctic water,
而北冰洋的冷水越过山脊
and cold water from the Arctic is flowing over this ridge
流入北大西洋
down into the North Atlantic,
然后从海底填满深海
and it's filling up the deep ocean from underneath.
而这就是世界上最大的瀑布
And this is the largest waterfall in the world.
它有3.5千米高
It's 3.5 kilometres high.
流经的水量
The amount of water going over it
是陆地上最大瀑布的两百倍
is 200 times bigger than the largest waterfall on land.
每秒五百万立方米的水
So, that's 5 million cubic metres every second,
流经这里
is pouring over this.
而我喜欢的一个点是
And the thing I love about this
几个世纪以来 水手们航行在
is that sailors have been crossing
冰岛和格陵兰岛之间 却从来不知道
from Iceland to Greenland for centuries and they've never known
在他们下面有如此巨大的瀑布
that this enormous waterfall was just underneath them.
但并不只是这里
But it's not just happening here.
冰冷的两极海水充满了
Cold polar water is filling up the deep ocean basins
全世界的海底
all around the world.
所以 深海其实很冷就是这个原因
So, this is the reason that the deep ocean is actually really cold.
现在我们可以回到刚才
So, now we can get back to the question
关于格陵兰鲨的问题
of that Greenland shark.
它在墨西哥湾做什么
What was it doing in the Gulf of Mexico?
它在那里的原因是
And the reason it was there is that the Gulf of Mexico,
来自极地的冷水充满了墨西哥湾的深处
really deep down, is filled up by cold water from the poles
并且保存在海底
that stays at the bottom.
发现它的地方只有四摄氏度
Where it was discovered, it was only four degrees Celsius,
而海表温度有二十八摄氏度
even though at the surface it was 28 degrees C.
所以海洋有两个主要的水层
So, we've got these two major layers in the ocean.
上面是暖水层
We've got the warmer layer on top,
就是我们看过的那幅美丽的海表温度地图
which is all of that beautiful surface map that we saw before.
但绝大部分深海盆地都充满了
But most of the deep ocean basins are filled up with cold water
从两极来的冷水
that came originally from the poles.
这是非常重要的海洋结构
That's a really important thing about the structure of the ocean.
我喜爱地图 但是它们让我烦恼的一点是
Now, I love maps, but they do annoy me in one respect,
它们展现的陆地是静止的
which is that they show the land as being stationary -
的确如此 这都没关系
which it is - that's all fine.
但是海洋也是静止的 事实却并非如此
But they also show the ocean as being still, and it really isn't.
海洋是流动的
It's moving.
如果你记得开始时
If you remember those beautiful swirls
那些温度地图上的美丽漩涡
on the temperature patterns at the start,
它们看起来是流动的
it looks like they're moving.
这里蕴含巨大的能量
There's lots of energy there.
我们已经习惯了大气气候的概念
So, we're used to the idea of atmospheric weather.
正如我们走出室外
That's what happens when we go outside
发现下雨了或者什么的
and we get rained on or whatever.
那海洋气候的概念呢
What about the idea of ocean weather?
为了谈谈海洋气候的概念
So, to talk to us about ocean weather,
让我们有请埃莉诺·富丽卡-威廉姆斯博士
please welcome Dr Eleanor Frajka-Williams.
你好
Hello.
首先 你不能来到现场
So, first of all, you can't join us in person,
但你有很好的理由 告诉我们是什么
but you've got a very good excuse for that. Tell us why that is.