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1º ESO/HOW DO OCEAN CURRENTS WORK - Contenido educativo

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Subido el 15 de marzo de 2021 por Alicia M.

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In 1992, a cargo ship carrying bath toys got caught in a storm. 00:00:00
Shipping containers washed overboard, 00:00:12
and the waves swept 28,000 rubber ducks and other toys into the North Pacific. 00:00:14
But they didn't stick together. 00:00:20
Quite the opposite. 00:00:22
The ducks have since washed up all over the world, 00:00:24
and researchers have used their paths to chart a better understanding of ocean currents. 00:00:26
Ocean currents are driven by a range of sources—the wind, tides, changes in water density, and 00:00:32
the rotation of the Earth. 00:00:40
The topography of the ocean floor and the shoreline modifies those motions, causing 00:00:43
currents to speed up, slow down, or change direction. 00:00:48
Ocean currents fall into two main categories—surface currents and deep ocean currents. 00:00:52
Surface currents control the motion of the top 10% of the ocean's water, while deep 00:00:58
ocean currents mobilize the other 90%. 00:01:03
Though they have different causes, surface and deep ocean currents influence each other 00:01:06
in an intricate dance that keeps the entire ocean moving. 00:01:11
Near the shore, surface currents are driven by both the wind and tides, which draw water 00:01:15
back and forth as the water level falls and rises. 00:01:20
Meanwhile, in the open ocean, wind is the major force behind surface currents. 00:01:24
As wind blows over the ocean, it drags the top layers of water along with it. 00:01:29
That moving water pulls on the layers underneath, and those pull on the ones beneath them. 00:01:34
In fact, water as deep as 400 meters is still affected by the wind at the ocean's surface. 00:01:39
If you zoom out to look at the patterns of surface currents all over the Earth, you'll 00:01:47
we'll see that they form big loops called gyres, 00:01:51
which travel clockwise in the northern hemisphere 00:01:55
and counterclockwise in the southern hemisphere. 00:01:57
That's because of the way the Earth's rotation affects the wind patterns 00:02:00
that give rise to these currents. 00:02:04
If the Earth didn't rotate, 00:02:06
air and water would simply move back and forth 00:02:08
between low pressure at the equator and high pressure at the poles. 00:02:10
But as the Earth spins, 00:02:14
air moving from the equator to the north pole is deflected eastward, 00:02:16
and air moving back down is deflected westward. 00:02:21
The mirror image happens in the southern hemisphere 00:02:24
so that the major streams of wind form loop-like patterns around the ocean basins. 00:02:27
This is called the Coriolis effect. 00:02:32
The winds push the ocean beneath them into the same rotating gyres, 00:02:35
and because water holds onto heat more effectively than air, 00:02:40
these currents help redistribute warmth around the globe. 00:02:43
Unlike surface currents, deep ocean currents are driven primarily by changes in the density 00:02:48
of seawater. 00:02:53
As water moves towards the North Pole, it gets colder. 00:02:55
It also has a higher concentration of salt, because the ice crystals that form trap water 00:02:58
while leaving salt behind. 00:03:04
This cold, salty water is more dense, so it sinks, and warmer surface water takes its 00:03:06
place, setting up a vertical current called thermohaline circulation. 00:03:11
circulation of deep water and wind-driven surface currents combine to form a winding 00:03:17
loop called the global conveyor belt. 00:03:23
As water moves from the depths of the ocean to the surface, it carries nutrients that 00:03:26
nourish the microorganisms which form the base of many ocean food chains. 00:03:30
The global conveyor belt is the longest current in the world, snaking all around the globe, 00:03:35
but it only moves a few centimeters per second. 00:03:41
It could take a drop of water a thousand years to make the full trip. 00:03:45
However, rising sea temperatures are causing the conveyor belt to seemingly slow down. 00:03:49
Models show this causing havoc with weather systems on both sides of the Atlantic, 00:03:55
and no one knows what would happen if it continues to slow, or if it stopped altogether. 00:03:59
The only way we'll be able to forecast correctly and prepare accordingly 00:04:05
will be to continue to study currents and the powerful forces that shape them. 00:04:09
What about the creatures that adapted to survive in these swirling seas? 00:04:15
Take a closer look at some truly fascinating ocean dwellers 00:04:20
with these two animations. 00:04:23
Subido por:
Alicia M.
Licencia:
Dominio público
Visualizaciones:
71
Fecha:
15 de marzo de 2021 - 18:04
Visibilidad:
Público
Centro:
IES LA SENDA
Duración:
04′ 34″
Relación de aspecto:
1.78:1
Resolución:
1920x1080 píxeles
Tamaño:
121.98 MBytes

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