Oceanography 15.1• Objectives

– Understand how density of the ocean is affected by temperature and how this results in currents.

– Coriolis Effect on ocean currents

– Climactic influence on circulation

– Technology types used to study ocean data.

Vocabulary

Oceanography Sonar

Salilnity thermocline

Upwelling density current

surface current

Section 15.1 Main Ideas• Oceanography is the scientific

study of Earth’s oceans.

• Oceans explored by:

– Sonar– Satellites– Submersibles

Scientists theorize that:

• First oceans formed over 4 billion years ago

– Some water from impacting comets – From deep within Earth’s interior released by

volcanism.

Section 15.1 Study Guide

Section 15.1 Main Ideas• Approx. 71% percent of Earth is covered

by oceans.

• Major oceans

– Pacific– Atlantic Major Oceans– Indian– Arctic– Antarctic.

Section 15.1 Main Ideas• Pacific - Largest, contains half of all seawater and is

larger than all Earth’s landmasses combined.

• Atlantic - extends from Antarctica to the arctic circle

• Indian - located mainly in the southern hemisphere.

Section 15.2 Main Ideas• Seawater

– 96.5 % water & 3.5% salt.

– Avg. salinity- 35 ppt.

• Ocean surface temps are –2°C to 30°C.

• Seawater density changes when salinity and/or temperature change.

Section 15.2 Study Guide

Ocean Temperatures• Temperatures

decrease with depth.

• 3 layers of the ocean:

– Epilimnion: surface layer

– Thrermocline = transitional ocean layer that lies between warm and cold layers

– Hypolimnion: Deep Zone.

Ocean Temperatures and Circulation• Density Currents

– As sea ice forms, most salt is forced out of the freezing water.

– The cold water around the ice becomes saltier and denser and sinks

– Cold water moves toward the equator along the ocean floor

http://www.earthgeu.com/

Other Currents• Wind-driven surface currents affect the upper

few hundred meters of the ocean.

– Upwelling occurs when winds push surface water aside and the surface water is replaced by cold, deep water.

– El Nino - when this upwelling fails to occur in the pacific ocean off the coast of South America.• Alters weather patterns around the world• Believed to reduce the number of hurricanes in the

Atlantic

Gyres (“J-eye-ers”)

– The oceans contain closed circular current systems, called gyres.

5 major gyres:

1. North Pacific

2. North Atlantic

3. South Pacific

4. South Atlantic

5. Indian Ocean

– What direction do the gyres turn?

– What might cause this?

11 22

33 44 55

15.2 Waves and Tides

Objectives

• Formation and breaking of waves

• Explain the formation of tides and compare neap versus spring tides.

Vocabulary

Crest Through

Wavelength Wave

Neap Tide Spring Tide

Breaker

Ocean Waves• Ocean waves caused by wind. Wave - rhythmic movement that carries

energy through matter or space

• Water in a wave moves in a circular motion; It does not move forward.

• When waves reach shallow water, friction with the bottom slows them, and they break.

• Breaker - collapsing wave that forms when a wave reaches shallow water

Section 15.3 Study Guide

Ocean Tides• Caused by gravitational

attraction among Earth, Moon, and Sun.

– Lunar tides are twice as high as solar tides.

Spring tides •Sun, Moon, Earth aligned•high tides - higher than normal•low tides - lower than normal.

Neap tides•high tides - lower than normal•low tides - higher than normal.

Neap Tide

Spring Tide

Spring Tide

1. Approximately how much of Earth’s surface is covered by oceans?

a. 51 percent c. 71 percent

b. 61 percent d. 81 percent

Multiple Choice

Chapter Assessment

Because most landmasses are located in the northern hemisphere, oceans cover only 61 percent of the surface there. However, 81 percent of the southern hemisphere is covered by water.

2. Of the areas listed below, which generally has the lowest ocean salinity?

a. subtropical regions c. temperate regions

b. tropical regions d. polar regions

In the polar regions, seawater is diluted by melting sea ice. On a localized level, the lowest salinities often occur where large rivers empty into the oceans.

Multiple Choice

Chapter Assessment

Multiple Choice

3. Which term below best describes the tide when the Sun, the Moon, and Earth form a right angle?

a. spring tide c. high tide

b. neap tide d. low tide

Chapter Assessment

During a neap tide, high tides are lower than normal and low tides are higher than normal. During a spring tide the solar and lunar tides are aligned, causing high tides to be higher than normal and low tides to be lower than normal. Spring and neap tides alternate every two weeks.

Multiple Choice

4. What is the average ocean surface temperature?

a. 8ºC c. 15ºC

b. 12ºC d. 18ºC

Chapter Assessment

Surface temperature of Earth’s oceans varies between –2ºC in the polar regions to 30ºC in equatorial regions.

Multiple Choice

5. Which of the following is the most prevalent ion in seawater?

a. chloride c. sodium

b. sulfate d. magnesium

Chapter Assessment

Chloride has a concentration of 19.35 ppt in seawater. It is followed by sodium (10.76 ppt), sulfate (2.71 ppt), and magnesium (1.29 ppt).

Short Answer

6. What are the three factors that determine wave height?

Chapter Assessment

The three factors that determine wave height are wind speed, wind duration, and fetch. Fetch refers to the expanse of water that the wind blows across.

Short Answer

7. What are the three basic ocean layers and are they distributed evenly throughout the oceans?

Chapter Assessment

The three basic ocean layers are the surface layer, the thermocline, and the bottom layer. They are not distributed evenly. Both the thermocline and surface layer are absent in polar seas, where water temperatures are cold from top to bottom.

True or False

8. Identify whether the following statements are true or false.

______ Oceanography is usually considered to have started with the Meteor expedition.

______ Some water molecules in the atmosphere are

continually being destroyed by ultraviolet radiation from the Sun.

______ Blue light does not penetrate as far as red light

in the ocean.

______ The Moon and Earth revolve around a common

center of gravity.

Chapter Assessment

false

true

false

true

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