SAT OG 2016 Reading - Test 2 reading 5

Questions 43-52 are based on the following

This passage is adapted from Geoffrey Giller ,“ Long a Mystery, How 500-Meter-High Undersea Waves Form Is Revealed.”© 2014 by Scientific American.

Some of the largest ocean waves in the world are

nearly impossible to see. Unlike other large waves,

these rollers, called internal waves, do not ride the
ocean surface. Instead, they move underwater ,
5 undetectable without the use of satellite imagery or

sophisticated monitoring equipment. Despite their

hidden nature, internal waves are fundamental parts

of ocean water dynamics, transferring heat to the

ocean depths and bringing up cold water from below.
10 And they can reach staggering heights—some as tall

as skyscrapers.
Because these waves are involved in ocean mixing

and thus the transfer of heat, understanding them is

crucial to global climate modeling, says Tom
15 Peacock, a researcher at the Massachusetts Institute

of Technology. Most models fail to take internal

waves into account .“ If we want to have more and

more accurate climate models, we have to be able to

capture processes such as this, ”Peacock says.
20 Peacock and his colleagues tried to do just that.

Their study, published in November in Geophysical

Research Letters, focused on internal waves generated

in the Luzon Strait, which separates Taiwan and the

Philippines. Internal waves in this region, thought to
25 be some of the largest in the world, can reach about

500 meters high. “That’ s the same height as the

Freedom Tower that’s just been built in New York,”

Peacock says.
Although scientists knew of this phenomenon in
30 the South China Sea and beyond, they didn’t know

exactly how internal waves formed. To find out,

Peacock and a team of researchers from M.I.T. and

Woods Hole Oceanographic Institution worked with

France’s National Center for Scientific Research
35 using a giant facility there called the Coriolis

Platform. The rotating platform, about 15 meters

(49.2feet) in diameter, turns at variable speeds and

can simulate Earth’s rotation. It also has walls, which

means scientists can fill it with water and create
40 accurate, large-scale simulations of various

oceanographic scenarios.
Peacock and his team built a carbon-fiber resin

scale model of the Luzon Strait, including the islands

and surrounding ocean floor topography. Then they
45 filled the platform with water of varying salinity to

replicate the different densities found at the strait,

with denser, saltier water below and lighter, less

briny water above. Small particles were added to the

solution and illuminated with lights from below in
50 order to track how the liquid moved. Finally, they

re-created tides using two large plungers to see how

the internal waves themselves formed.
The Luzon Strait’s underwater topography, with a

distinct double-ridge shape, turns out to be
55 responsible for generating the underwater waves.

As the tide rises and falls and water moves through

the strait, colder, denser water is pushed up over the

ridges into warmer, less dense layers above it.

This action results in bumps of colder water trailed
60 by warmer water that generate an internal wave.

As these waves move toward land, they become

steeper—much the same way waves at the beach

become taller before they hit the shore —until they

break on a continental shelf.
65 The researchers were also able to devise a

mathematical model that describes the movement

and formation of these waves. Whereas the model is

specific to the Luzon Strait, it can still help

researchers understand how internal waves are
70 generated in other places around the world.

Eventually, this information will be incorporated into

global climate models, making them more accurate.

“It’s very clear, within the context of these [global

climate] models, that internal waves play a role in
75 driving ocean circulations ,” Peacock says.

Question 43 The first paragraph serves mainly to