Chapter 13 Oceans. Chapter: Oceans Table of Contents Section 3: WavesWaves Section 1: Ocean Water Section 2: Ocean Currents and ClimateOcean Currents.

Chapter 13

Oceans

Chapter: Oceans

Table of ContentsTable of Contents

Section 3: Waves

Section 1: Ocean Water

Section 2: Ocean Currents and Climate

Section 4: Life in the Oceans

A. Surface Currents1. Ocean water never stands still. Currents

move the water from place to place constantly.

Ocean Currents and ClimateOcean Currents and Climate

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A. Surface Currents2. They exist both at the ocean’s surface and

in deeper water.


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B. Causes of Surface Currents1. 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.


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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.


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C. The Gulf Stream3. Currents on eastern coasts of continents, like the

Gulf Stream, are usually warm, while currents on western coasts of continents are usually cold.


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D. Climate1. Locate Iceland

on the map.

2. Based on its location and its name, you might expect it to have a cold climate.


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D. Climate

4. The current’s warm water heats the surrounding air and keeps Iceland’s climate mild and its harbors ice free year-round.


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3. However, the Gulf Stream flows past Iceland.

E. Cold Surface Currents


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1. Find the California Current off the west coast of North America and the Peru Current alongthe west coast of South America. It carries cold water from polar regions toward the equator.

E. Cold Surface Currents

3. San Francisco has cool summers and many foggy days because of the California Currents.


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2. Cold surface current affect the climate of coastal cities.

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.


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G. Cold and Salty Water1. 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.


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3. It sinks and slowly flows along the ocean floor toward the southern Atlantic Ocean.

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.


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H. Density Currents and Climate Change

1. If Earth’s temperature rose enough, ice couldn’t easily form near the polar regions.


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2. Freshwater from melting glaciers on land also could reduce the salinity of the ocean water.

H. Density Currents and Climate Change


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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.

I. Upwelling1. An upwelling is a current in the ocean that

brings deep, cold water to the ocean surface.


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2. This occurs along some coasts where winds cause surface water to move away from the land.

I. Upwelling


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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.

I. Upwelling


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5. The cold water is full of nutrients from dead, decayed organisms. Tiny marine organisms

thrive in these nutrient-rich 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.

J. El Niño1. 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.


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2.Without nutrients provided by upwelling, fish and other organisms cannot find food. Thus, the rich fishing grounds off of Peru are disrupted.

Section CheckSection Check

22Question 1

Which way do currents rotate in the southern hemisphere?


22Question 2

Explain how the climate of different regions is affected by ocean currents.


22Question 3

What type of current exists in the Mediterranean Sea?

A. cold surface currentB. density currentC. surface currentD. upwelling

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Chapter 13 Oceans. Chapter: Oceans Table of Contents Section 3: WavesWaves Section 1: Ocean Water Section 2: Ocean Currents and ClimateOcean Currents.

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