Transcript A. Surface Currents

Chapter 13
Oceans
Table of Contents
Chapter: Oceans
Section 1: Ocean Water
Section 2: Ocean Currents and Climate
Section 3: Waves
Section 4: Life in the Oceans
Ocean Currents and Climate
2
A. Surface Currents
1. Ocean water never stands still. Currents
move the water from place to place constantly.
Ocean Currents and Climate
2
A. Surface Currents
2. They exist both at the ocean’s surface and
in deeper water.
Ocean Currents and Climate
2
B. Causes of Surface Currents
1. surface currents are powered by wind and
usually move only the upper few hundred
meters of seawater.
2. Because of Earth’s rotation, ocean currents
do not move in straight lines.
3. Earth’s rotation causes surface ocean
currents in the northern hemisphere to curve
to the right and surface ocean currents in the
southern hemisphere to curve to the left.
Ocean Currents and Climate
2
C. The Gulf Stream
1. One of the most important currents for sailing
east across the North Atlantic Ocean is the
Gulf Stream.
2. The Gulf Stream flows from Florida
northeastward toward North Carolina. There
it curves toward the east and becomes slower
and broader.
Ocean Currents and Climate
2
C. The Gulf Stream
3. Currents on eastern coasts of continents, like the
Gulf Stream, are usually warm, while currents on
western coasts of continents are usually cold.
Ocean Currents and Climate
2
D. Climate
1. Locate Iceland
on the map.
2. Based on its
location and its
name, you
might expect it
to have a cold
climate.
Ocean Currents and Climate
2
D. Climate
3. However, the Gulf Stream flows past Iceland.
4. The current’s
warm water
heats the
surrounding air
and keeps
Iceland’s
climate mild and
its harbors ice
free year-round.
Ocean Currents and Climate
2
E. Cold Surface Currents
1. Find the
California
Current off the
west coast of
North America
and the Peru
Current along
the west coast of South America. It carries
cold water from polar regions toward the
equator.
Ocean Currents and Climate
2
E. Cold Surface Currents
2. Cold surface
current affect
the climate
of coastal
cities.
3. San Francisco has cool summers and many
foggy days because of the California Currents.
Ocean Currents and Climate
2
F. Density Currents
1. A density current forms when a mass of
dense seawater sinks beneath less dense
seawater.
2. Seawater becomes more dense when it gets
colder or becomes more salty.
3. Changes in temperature and salinity work
together to create density currents. A density
current moves very slowly.
Ocean Currents and Climate
2
G. Cold and Salty Water
1. An important density current that affects
many regions of Earth’s oceans begins north
of Iceland.
2. When water freezes, dissolved salts are left
behind in the unfrozen water which is very
dense because it is cold and salty.
3. It sinks and slowly flows along the ocean
floor toward the southern Atlantic Ocean.
Ocean Currents and Climate
2
G. Cold and Salty Water
4. As the water is
sinking near
Iceland, warm
surface water of
the Gulf Stream,
shown in red,
moves northward
from the equator
to replace it.
Ocean Currents and Climate
2
H. Density Currents and Climate
Change
1. If Earth’s temperature rose enough, ice
couldn’t easily form near the polar regions.
2. Freshwater from melting glaciers on land
also could reduce the salinity of the ocean
water.
Ocean Currents and Climate
2
H. Density Currents and Climate
Change
3. The density currents would weaken or stop. If
density currents stopped flowing southward,
warm equatorial surface water would no longer
flow northward.
4. Earth could face drastic climate shifts,
including changing rainfall patterns and
temperatures.
Ocean Currents and Climate
2
I. Upwelling
1. An upwelling is a current in the ocean that
brings deep, cold water to the ocean
surface.
2. This occurs along some coasts where winds
cause surface water to move away from the
land.
Ocean Currents and Climate
2
I. Upwelling
3. Notice that when surface water is pushed
away from the coast, deep water rises to the
surface to take its
place.
4. This cold, deep
water continually
replaces the surface
water that is pushed
away from the
coast.
Ocean Currents and Climate
2
I. Upwelling
5. The cold water is full of nutrients from dead,
decayed organisms. Tiny marine organisms
thrive in these nutrientrich areas, which, in turn,
attract many fish. As a
result, areas of upwelling
are important fishing
grounds because fish are
attracted to the areas to
eat the organisms.
Ocean Currents and Climate
2
J. El Niño
1. During an El Niño (el NEEN yoh) event,
the winds blowing water from the coast of
Peru slow down. The Eastern Pacific Ocean
becomes warmer, and upwelling is reduced
or stops.
2.Without nutrients provided by upwelling,
fish and other organisms cannot find food.
Thus, the rich fishing grounds off of Peru
are disrupted.
Section Check
2
Question 1
Which way do currents rotate in the southern
hemisphere?
Section Check
2
Question 2
Explain how the climate of different regions
is affected by ocean currents.
Section Check
2
Question 3
What type of current exists in the
Mediterranean Sea?
A. cold surface current
B. density current
C. surface current
D. upwelling
Help
To advance to the next item or next page click on any
of the following keys: mouse, space bar, enter, down or
forward arrow.
Click on this icon to return to the table of contents
Click on this icon to return to the previous slide
Click on this icon to move to the next slide
Click on this icon to open the resources file.
Click on this icon to go to the end of the presentation.
End of Chapter Summary File