Download All You Need to Know About Gyres

Name:______________________________________________________
Date:_______________________________
All You Need to Know About Gyres
Per:_________________
1. The Formation of Gyres:
a. How does a gyre form? = A natural phenomenon of a rotating current system. Tropical gyres form near the Equator.
b. What are the three forces that cause circulation of the gyre? = Three forces cause the circulation of a gyre: global wind
patterns, Earth’s rotation, and Earth’s landmasses. Wind drags on the ocean surface, causing water to move in the direction the
wind is blowing.
c. Explain ALL THREE in detail.
i. Global wind patterns = the earth rotates on its axis from west to east. This rotation causes both the wind and ocean
currents to move from east to west. Thus, the wind movement and ocean currents in the northern hemisphere rotate
clockwise and counter clockwise in the southern hemisphere.
ii. Earth’s rotation- The Earth’s rotation deflects, or changes the direction of, these wind-driven currents. This deflection is a
part of the Coriolis effect. The Coriolis effect shifts surface currents by angles of about 45 degrees.
iii. Earth’s landmasses- In addition to surface currents, water also moves vertically as deeper water rises toward shallower
depths. This is referred to as Upwelling. Upwelling can occur during an event where warmer surface waters and air
temperatures are blown from the western coasts of South America toward Indonesia and Australia (an La Nina). Deeper
water from below rises toward the surface, replacing the horizontally moving water. The upwelling water is cooler and
nutrient rich, causing a decrease in air temperatures near the surface.
d. How do landmasses affect gyres? Answer above.
** Trade Winds: In the Northern Hemisphere, warm air around the equator rises and flows north toward the pole. As the air moves
away from the equator, the Coriolis effect deflects it toward the right. It cools and descends near 30 degrees North latitude. The
descending air blows from the northeast to the southwest, back toward the equator. A similar wind pattern occurs in the Southern
Hemisphere; these winds blow from the southeast toward the northwest and descend near 30 degrees South latitude.
These prevailing winds, known as the trade winds, meet at the Intertropical Convergence Zone (also called the doldrums) between
5 degrees North and 5 degrees South latitude, where the winds are calm. The remaining air (air that does not descend at 30
degrees North or South latitude) continues toward the poles and is known as the westerly winds, or westerlies.
2. The Coriolis effect
a. What is the Coiolis effect? The Coriolis effect is an inertial force that shifts surface currents by angles of about 45 degrees. In
the Northern Hemisphere, ocean currents are deflected to the right, in a clockwise motion. In the Southern Hemisphere, ocean
currents are pushed to the left, in a counterclockwise motion.
b. In the Coriolis effect, explain why currents don’t follow wind directions? The Earth rotates faster at the Equator than it does
at the poles. This is because the Earth is wider at the Equator. A point on the Equator has farther to travel in a day. In the Northern
Hemisphere, wind from high-pressure systems pass low-pressure systems on the right. This causes the system to swirl counterclockwise. Low-pressure systems usually bring storms. This means that hurricanes and other storms swirl counter-clockwise in
the Northern Hemisphere. In the Southern Hemisphere, storms swirl clockwise.
c. What is the relationship between the current direction and wind direction? Coastal currents are affected by local winds.
Surface ocean currents, which occur on the open ocean, are driven by a complex global wind system. To understand the effects of
winds on ocean currents, one first needs to understand the Coriolis force and the Ekman spiral.
d. Which direction does the earth rotate? From west to east. Which direction do the currents rotate in each hemisphere of
the earth? = In the Northern Hemisphere, ocean currents are deflected to the right, in a clockwise motion. In the Southern
Hemisphere, ocean currents are pushed to the left, in a counterclockwise motion.
** Important info: At the equator, there is no Coriolis effect so there is very little to no deflection.
3. The Ekman spiral
a. Explain the Ekman spiral. The Ekman spiral occurs as a consequence of the Coriolis effect. When surface water molecules are
moved by the wind, they drag deeper layers of water molecules below them. Like surface water, the deeper water is deflected by
the Coriolis effect—to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. As a result, each
successively deeper layer of water moves more slowly to the
right or left, creating a spiral effect.
b. How is water pulled up from the lower levels? Each layer
of water molecules is moved by friction from the shallower
layer, and each deeper layer moves more slowly than the
layer above it, until the movement ceases at a depth of about
100 meters (330 feet). Like the surface water, however, the
deeper water is deflected by the Coriolis effect—to the right
in the Northern Hemisphere and to the left in the Southern
Hemisphere. As a result, each successively deeper layer of
water moves more slowly to the right or left, creating a spiral
effect. Because the deeper layers of water move more slowly
than the shallower layers, they tend to “twist around” and
flow opposite to the surface current.
c. How deep does it typically go? = Spiral pattern descending
about 100 meters (330 feet).
d. Where can you find them? Near a horizontal boundary in
which the flow direction rotates as one moves away from the
boundary
4. Tropical Gyre (info found at: http://education.nationalgeographic.com/education/encyclopedia/ocean-gyre/?ar_a=1)
a. Why is this Gyre different from the 5 major Gyres? Winds are the primary creators of currents (not the earth rotation meaning the
Coriolis) Their for the Coriolis effect is not found at the Equator. Tropical gyres flow in straighter line following an east-west pattern.
b. Where can this Gyre be found? This Gyre forms near the Equator and near the northern and southern Indian Ocean Gyres
c. Which direction does this Gyre typically rotate? They don’t typically form a circular patterns. Tropical gyres flow in straighter line
following an east-west pattern.
5. Subtropical Gyre (info found at: http://education.nationalgeographic.com/education/encyclopedia/ocean-gyre/?ar_a=1)
a. Why is this Gyre different from the 5 major Gyres? form at higher latitudes
b. Where can this Gyre be found? In polar and equatorial regions of Earth, & circle areas beneath regions of high atmospheric pressure.
c. Which direction does this Gyre typically rotate? In the Northern Hemisphere, ocean currents are deflected to the right, in a clockwise
motion. In the Southern Hemisphere, ocean currents are pushed to the left, in a counterclockwise motion.
d. What can be found at the center of this Gyre? A buildup of water/ a high-pressure area that is surrounded by water moving in either
clockwise or counterclockwise rotation.
6. Sub-polar Gyre (info found at: http://education.nationalgeographic.com/education/encyclopedia/ocean-gyre/?ar_a=1)
a. Why is this Gyre different from the 5 major Gyres? Circulation of surface wind and ocean water is counterclockwise in the Northern
Hemisphere, around a low-pressure area sub polar gyres away from coastal areas. These surface currents are replaced by cold, nutrientrich water in a process called upwelling.
b. Where can this Gyre be found? Bounded by islands such as Iceland, Greenland, and the Aleutians; and the northern reaches
of Scandinavia, Asia, and North America. (In the polar regions of the planet)
c. Which direction does this Gyre typically rotate? Circulation of surface wind and ocean water is counterclockwise in the Northern
Hemisphere, around a low-pressure area sub polar gyres away from coastal areas.
d. What can be found at the center of this Gyre? A low pressure area sits beside it.
7. North Atlantic Ocean Gyre (One of the 5 major Gyres)
a. What direction does it rotate? Why? In the Northern Hemisphere, ocean currents are deflected to the right, in a clockwise motion
because of Coriolis effect.
b. What continents does it border? North Atlantic from near the equator almost to Iceland, and from the east coast of North America to
the west coasts of Europe and Africa.
c. What currents compose, or run through, this Gyre? Gulf Stream in the west, the North Atlantic Current in the north, the Canary
Current in the east, and the Atlantic North Equatorial Current in the south
d. What forms at the center of this Gyre? The North Atlantic Garbage Patch
8. South Atlantic Ocean Gyre (One of the 5 major Gyres)
a. What direction does it rotate? Why? Counter clockwise in the southern hemisphere because of the Coriolis effect.
b. What continents does it border? Antarctica, the south western part of Africa and the east part of South America.
c. What currents compose, or run through, this Gyre? Antarctic Circumpolar Current, Brazil Current, and the Gulf Stream
d. What forms at the center of this Gyre? Massive amount of debris forming another garage patch
9. North Pacific Ocean Gyre (One of the 5 major Gyres)
a. What direction does it rotate? Why? In the Northern Hemisphere, ocean currents are deflected to the right, in a clockwise
motion because of Coriolis effect.
b. What continents does it border? Western United states (Cali.) and Asia (Japan)
c. What currents compose, or run through, this Gyre? The North Pacific Current to the north, the California Current to the east,
the North Equatorial Current to the south, and the Kuroshio Current to the west.
d. What forms at the center of this Gyre? The Great Pacific Garbage Patch
10. South Pacific Ocean Gyre (One of the 5 major Gyres)
a. What direction does it rotate? Why? Counter clockwise in the southern hemisphere because of the Coriolis effect.
b. What continents does it border? It is boarded by equator to the north, Australia to the west, the Antarctic Circumpolar Current
to the south, and South America.
c. What currents compose, or run through, this Gyre? It borders the Antarctic Circumpolar Current to the south.
d. What forms at the center of this Gyre? A Garbage Patch
11. Indian Ocean Gyre (One of the 5 major Gyres)
a. What direction does it rotate? Why? Normally moving counter-clockwise, in the winter the Indian Ocean gyre reverses direction
due to the seasonal winds of the South Asian Monsoon. In the summer, the land is warmer than the ocean, so surface winds blow
from the ocean to the land. However, during the winter, these temperatures reverse, making the winds blow from the land to the
ocean.
b. What continents does it border? Australian side to the African side, down the African coast
c. What currents compose, or run through, this Gyre? South Equatorial Current and the West Australian Current
d. What forms at the center of this Gyre? The Indian Ocean Garbage Patch
12. Gyre Garbage Patches
a. How does it form? The circular motion of the gyre draws in the debris, mostly small particles of plastic. Eventually, the debris
makes its way to the center of the gyre, where it becomes trapped and breaks down into a kind of plastic soup. Ocean gyres circle
large areas of stationary, calm water. Debris drifts into these areas and, due to the region’s lack of movement, can accumulate for
years.
b. Where does it form and where are they found? he Indian Ocean, North Atlantic Ocean, and North Pacific Ocean
c. Scientists are studying the degradation, or breakdown, of plastic. Why is this bad. Unlike natural substances, such as wood
or metal, plastic does not disintegrate into organic substances. It simply breaks down into smaller and smaller pieces of plastic.
d. What happens to the plastic that gets stuck in these “Garbage Patches”? These tiny plastic particles are as small as
the algae and plankton that form the basis of the entire ocean food web. Species such as shrimp, birds, and fish consume these
micro-plastics, which oftentimes kills them. The plastic chemicals can also be absorbed by predators of these species.
The concentration of these chemicals increases through each trophic level of the food chain, a process known as bio-magnification.
e. Who is taking responsibility for the mess? NO ONE IN PARTICULAR. NO ONE IS TAKING BLAME.