NASA Sees Tides Under the Ocean's Surface

Narration: Kathleen Gaeta

Transcript:

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Tides are a complicated

phenomenon.

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Tides in the ocean are generated

by the moon's gravitational

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pull, and they affect more than

just how much room on the beach

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there is for a chair and

umbrella. They're actually long

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period waves that move through

the oceans in response to forces

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exerted by the moon and sun,

making their way towards the

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coastlines, where they appear as

the regular rise and fall of the

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sea surface.

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And they may also help to slow

down the rate of global warming

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of the atmosphere, partially by

forming a complex system of

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underwater waves that can help

move heat into the ocean

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interior. That complex system of

waves is essentially a different

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type of tide, called Internal Tides.

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NASA can see how Internal Tides

move and flow in the ocean here.

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Across a long swath of the North

Pacific Ocean sits the Hawaiian

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Ridge, a massive underwater

structure high enough in a few

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places to reach the ocean

surface and form the islands of

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our 50th state. The tidal

currents that are generated by

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the moon's gravitation impact

the Hawaiian Ridge, causing deep

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dense water to be forced upward.

Gravity and buoyancy forces then

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tug the water down and up again,

creating oscillations. Those

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oscillations are internal waves.

But since the waves oscillate at

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the tidal period, which is the

time it takes for tides to

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complete one cycle, from high to

low, and back to high again in

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roughly 12 hours, we call them

Internal Tides.

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Once generated along the ridge,

these internal tides move away

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from it, both northwards and

southwards, and can sometimes go

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as far as thousands of miles.

underneath the surface, the

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waves can be as big as hundreds

of feet. But on the ocean

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surface, they're often only a

few inches high, barely large

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enough to notice.

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Yet instruments on satellites,

like altimeters, are capable of

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measuring those small surface

waves, and NASA can predict

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Internal Tides based on years of

compiled satellite data.

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The ocean is filled with

underwater topography, from

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mountains to ridges to trenches,

creating many sources of

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Internal Tides all over the

global ocean and giving rise to

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the many complicated patterns

seen in this visualization.

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Although Internal Tides might

seem insignificant, being only a

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few inches on the ocean surface,

they provide oceanographers with

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a unique way to map and study

the much larger internal water

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motion. That water motion and

subsequent mixing between warm

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shallow water and cold deeper

water is thought to move heat

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from global warming of Earth's

atmosphere down into the ocean interior.

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In other words, Internal Tides

are an incredibly significant

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mechanism and have a sizable

impact on the Earth's climate.