How do ocean currents work? - Jennifer Verduin

翻译人员: Xu Xingruo 校对人员: Lipeng Chen

In 1992,

1992年，

a cargo ship carrying bath toys got caught in a storm.

一艘装载着洗浴玩具的货船 遭遇了风暴。

Shipping containers washed overboard,

货物被冲入海中，

and the waves swept 28,000 rubber ducks and other toys into the North Pacific.

海浪将28000只橡胶鸭 和其它玩具冲卷入北太平洋。

But they didn’t stick together.

但是它们没有集中在一起。

Quite the opposite–

恰恰相反——

the ducks have since washed up all over the world,

橡皮鸭被冲至世界各地，

and researchers have used their paths

而研究者则利用它们的漂流轨迹

to chart a better understanding of ocean currents.

绘制洋流图，以更好地了解它。

Ocean currents are driven by a range of sources:

洋流受到多个因素的驱使：

the wind, tides, changes in water density,

风、潮汐、海水的密度变化

and the rotation of the Earth.

和地球的自转。

洋底的地形和海岸线的形态 影响着洋流的动态

The topography of the ocean floor and the shoreline modifies those motions,

causing currents to speed up,

使它们或增速，

slow down, or change direction.

或减速，或改变方向。

洋流分为两种：

Ocean currents fall into two main categories:

表层流和深海洋流。

surface currents and deep ocean currents.

表层流控制着顶层10%的海水的动向，

Surface currents control the motion

of the top 10 percent of the ocean’s water,

while deep-ocean currents mobilize the other 90 percent.

而深海洋流驱动着其它90%的海水。

Though they have different causes,

虽然这两种洋流的成因不同，

surface and deep ocean currents influence each other

但这两种洋流相互影响，

in an intricate dance that keeps the entire ocean moving.

以一种复杂的舞蹈保持海水的涌动。

Near the shore,

近岸处，

surface currents are driven by both the wind and tides,

风和潮汐推动着表层流，

which draw water back and forth as the water level falls and rises.

使得海水随着海水位的升降 前进或后退。

Meanwhile, in the open ocean, wind is the major force behind surface currents.

同时，在开阔的洋面上， 风是驱动表层流的主要力量。

As wind blows over the ocean,

当风吹过洋面时，

it drags the top layers of water along with it.

顶层的海水随它流动。

That moving water pulls on the layers underneath,

流动的顶层海水带动了下层的海水，

and those pull on the ones beneath them.

下层的海水又带动了更下一层的海水。

In fact, water as deep as 400 meters

事实上，深至400米的海水

is still affected by the wind at the ocean’s surface.

仍受海水表面的风的影响。

If you zoom out to look at the patterns of surface currents all over the earth,

如果你身处高空， 观察世界各处洋流的流动模式，

you’ll see that they form big loops called gyres,

就会发现它们形成了 被称为“流涡”的巨大回路，

which travel clockwise in the northern hemisphere

在北半球顺时针流动，

and counter-clockwise in the southern hemisphere.

而在南半球逆时针流动。

That’s because of the way the Earth’s rotation

这是因为地球自转的方式

affects the wind patterns that give rise to these currents.

影响着造就洋流的大气环流。

If the earth didn’t rotate,

如果地球不自转，

air and water would simply move back and forth

大气和海水就只会

between low pressure at the equator

在赤道的低压带和两极的高压带之间

and high pressure at the poles.

来回移动。

But as the earth spins,

但实际上地球在自转，

air moving from the equator to the North Pole is deflected eastward,

从赤道吹向北极的风向东偏转，

and air moving back down is deflected westward.

而自北极向南吹的风向西偏转。

The mirror image happens in the southern hemisphere,

南半球的情况则像是个镜像翻转，

so that the major streams of wind

所以风的主流

form loop-like patterns around the ocean basins.

在海盆上形成了回路状的图案。

This is called the Coriolis Effect.

这就是所谓的“科里奥利效应”。

The winds push the ocean beneath them into the same rotating gyres.

流动的大气推动其下的海水 形成了同样的流涡。

And because water holds onto heat more effectively than air,

因为水比大气更容易吸收热量，

these currents help redistribute warmth around the globe.

所以洋流促进了热量 在全球范围内的流动。

Unlike surface currents,

与表层流不同，

deep ocean currents are driven primarily by changes in the density of seawater.

深海洋流的产生主要缘于 海水密度的变化。

As water moves towards the North Pole,

当海水向北极流动时，

it gets colder.

水温逐渐降低。

It also has a higher concentration of salt,

同时海水也有了更高的含盐量，

because the ice crystals that form trap water while leaving salt behind.

因为冰晶使水凝固，而盐仍留在水中。

This cold, salty water is more dense,

这种冷且含盐度高的海水的密度越来越高，

so it sinks,

所以它向下沉，

and warmer surface water takes its place,

而温暖的表层流取代了它的位置，

setting up a vertical current called thermohaline circulation.

这便形成了被称作“热盐环流”的垂直洋流。

Thermohaline circulation of deep water and wind-driven surface currents

由深层海水和受风驱使的表层流 构成的热盐循环

combine to form a winding loop called the Global Conveyor Belt.

构成了曲曲折折的回路——全球传送带。

As water moves from the depths of the ocean to the surface,

海水从洋底升至表层时，

it carries nutrients that nourish the microorganisms

携带着滋养微生物的营养物质，

which form the base of many ocean food chains.

而这些微生物正是许多海洋食物链的基础。

The global conveyor belt is the longest current in the world,

全球传送带是世界上最长的洋流，

snaking all around the globe.

蜿蜒环绕着整个地球。

But it only moves a few centimeters per second.

但它每分钟只移动几厘米。

It could take a drop of water a thousand years to make the full trip.

对于一滴海水来说， 做一次完整的旅行需要花上一千年。

However, rising sea temperatures are causing the conveyor belt

然而，上升的海平面似乎

to seemingly slow down.

使得传送带的速度慢了下来。

Models show this causing havoc with weather systems

相关模型显示，

这正对大西洋两岸的天气系统造成严重破坏，

on both sides of the Atlantic,

and no one knows what would happen if it continues to slow

而且人们无从得知，如果传导持续减慢，

or if it stopped altogether.

或干脆停下来的话，会有怎样的后果。

The only way we’ll be able to forecast correctly and prepare accordingly

正确预测并做好相应防备的唯一方法，

will be to continue to study currents and the powerful forces that shape them.

是持续研究洋流 和造就它们的巨大力量。