THE DYNAMIC OCEANCh. 16

16.1 Ocean CirculationSC.912.N.1.1, SC.912.N.2.5SC.912.E.6.5, SC.912.E.7.2, SC.912.E.7.3 , SC.912.E.7.4 , SC.912.E.7.9

Objectives

Explain how surface currents develop. Describe how ocean currents affect

climate. State the importance of upwelling. Describe the formation of density

currents.

Vocabulary

Ocean current Surface current Gyre Coriolis Effect Upwelling Density current

Essential Questions

1. How do surface currents develop?2. How do ocean currents affect climate?3. Why is upwelling important?4. How are density currents formed?

16.1 The Composition of Seawater

Ocean Currents 1 min videohttp://www.cleanvideosearch.com/media/action/yt/watch?videoId=3niR_-Kv4SM

Surface Circulation

Ocean current is the mass of ocean water that flows from one place to another.

Surface currents are movements of water that flow horizontally in the upper part of the ocean’s surface.

Surface currents develop from friction between the ocean and the wind that blows across its surface.

Ocean Surface Currents

Gyers

• Gyres are huge circular-moving current systems that dominate the surfaces of the oceans.

The Coriolis effect is the deflection of currents away from their original course as a result of Earth’s rotation.

Ocean Current & Climate

When currents from low-latitude regions move into higher latitudes, they transfer heat from warmer to cooler areas on Earth.

As cold water currents travel toward the equator, they help moderate the warm temperatures of adjacent land areas.

False-Colored Satellite Image of the Gulf Stream

Upwelling

Upwelling is the rise of cold water from deeper layers to replace warmer surface water.

Upwelling brings greater concentrations of dissolved nutrients, such as nitrates and phosphates, to the ocean surface.

Effects of Upwelling

Deep Ocean Circulation

Density currents are vertical currents of ocean water that result from density differences among water masses.

An increase in seawater density can be caused by a decrease in temperature or an increase in salinity.

Deep Ocean Circulation

High Latitudes Most water involved in deep-ocean currents begins

in high latitudes at the surface.

Evaporation Density currents can also result from increased

salinity of ocean water due to evaporation.

Cross Section of the Arctic Ocean

A Conveyor Belt

In a simplified model, ocean circulation is similar to a conveyor belt that travels from the Atlantic Ocean, through the Indian and Pacific Oceans, and back again.

Ocean Current Video 15 min.http://www.cleanvideosearch.com/media/action/yt/watch?videoId=Ca4eRt2wwg8

Essential QuestionsYou have 15 minutes to answer the questions from this section. Be prepared to discuss your answers.

How do surface currents develop?Surface currents develop from friction between the ocean and the wind that blows across its surface.

How do ocean currents affect climate?Warm water currents that come from equatorial regions transfer heat to cooler areas of Earth; for example the Gulf Stream and North Atlantic currents warm northwestern Europe in the winter months. Cold water currents from the poles moderate warm temperatures of adjacent land areas.

Why is upwelling important?Upwelling brings dissolved nutrients to the ocean surface, providing the necessary nutrients for phytoplankton to undergo photosynthesis. This productivity supports the extensive populations of fish and other organisms.

How are density currents formed?They are formed when the density of water changes due to a change in salinity and temperature.

16.2 Waves & Tides

Objectives

Describe how ocean waves get energy. State three factors that determine

characteristics of a wave. Describe how energy moves through a

wave. Explain the forces that produce tides.

Vocabulary

Wave height Wave length Wave period Fetch

Tide Tidal range Spring tide Neap tide

Waves and Tides 9 min videohttp://www.cleanvideosearch.com/media/action/yt/watch?videoId=l1WF8b6HZLM

Wave Motion Demo

Purpose – Students will see that wave energy travels without causing individual particles of the medium to move very much.

Materials – Slinky toy Procedure – Have a student hold one end

of a slinky without moving it. Stretch the slinky out, gather a few rings together, release them all at once while still holding the end of the slinky in your hand.

Essential Questions

1. From where do ocean waves obtain energy?

2. What three quantities are used to describe a wave?

3. How does energy move by means of a wave?

4. What force produces tides?5. What are three typical tidal patterns?

Wave Characteristics

Most ocean waves obtain their energy and motion from the wind.

The wave height is the vertical distance between the trough and crest.

The wavelength is the horizontal distance between two successive crests or two successive troughs.

Anatomy of a Wave

Wave Characteristic

The wave period is the time it takes one full wave—one wavelength—to pass a fixed position.

Fetch is the distance that the wind has traveled across open water.

The height, length, and period that are eventually achieved by a wave depend on three factors: (1) wind speed, (2) length of time the wind has blown, and (3) fetch.

Wave Motion

Circular orbital motion allows energy to move forward through the water while the individual water particles that transmit the wave move around in a circle.

Breaking Waves

Changes occur as a wave moves onto shore. As the waves touch bottom, wave speed

decreases. The decrease in wave speed results in a decrease in wavelength and an increase in wave height.

Breaking Waves

Tides

Tides are daily changes in the elevation of the ocean surface.

Ocean tides result from the gravitational attraction exerted upon Earth by the moon and, to a lesser extent, by the sun.

Tide-Causing Forces The force that produces tides is gravity.

Tide Bulges on Earth Caused by the Moon

Tides

Tidal range is the difference in height between successive high and low tides.

Spring tides are tides that have the greatest tidal range due to the alignment of the Earth–moon–sun system.

Neap tides are tides that have the lowest tidal range, occurring near the times of the first-quarter and third-quarter phases of the moon.

Tides

SPRING TIDES NEAP TIDES

When the Earth, Moon, and Sun are aligned we experience Spring Tides.

New Moon & Full Moon

When Earth, Moon, and Sun are at right angles to each other, we experience Neap Tides.

First Quarter & Third Quarter

Earth–Moon–Sun Positionsand the Tides

Tidal Patterns

Three main tidal patterns exist worldwide: diurnal tides, semidiurnal tides, and mixed tides.

Essential QuestionsYou have 15 minutes to answer the questions from this section. Be prepared to discuss your answers.

From where do ocean waves obtain energy?Waves obtain their energy from wind.

What three quantities are used to describe a wave?Three qualities used to describe waves are: wind speed, the length of time the wind has blown, and fetch.

How does energy move by means of a wave?Circular motion allows energy to move forward through a wave, while the individual water particles that transmit the wave move around in a circle.

What force produces tides?Gravity is the force that produces tides.

What are three typical tidal patterns?The three tidal patterns are: diurnal, semidiurnal, and mixed.

16.3 Shoreline Processes & FeaturesSC.912.N.1.1, SC.912.N.2.5SC.912.E.6.5, SC.912.E.7.2, SC.912.E.7.3 , SC.912.E.7.4 , SC.912.E.7.9

Objectives

List the agents responsible for the movement of sediments along the shoreline.

Explain how refraction affects wave action along the shore.

Describe the processes that form shoreline features.

List the structures that can be built to protect a shoreline.

Vocabulary

Beach Wave refraction Longshore currents Barrier islands

Essential Questions

1. How does refraction affect wave action along the shore?

2. What do longshore currents do?3. By which processes do shoreline features

form?4. What structures can be built to protect a

shoreline?5. What is beach nourishment?

Forces acting on the shoreline

A beach is the accumulation of sediment found along the shore of a lake or ocean.

Waves along the shoreline are constantly eroding, transporting, and depositing sediment. Many types of shoreline features can result from this activity.

Forces acting on the shoreline

WAVE IMPACT ABRASION

The impact of large, high-energy waves against the shore can be awesome in its violence. Each breaking wave may hurl thousands of tons of water against the land, sometimes causing the ground to tremble.

Abrasion is the sawing and grinding action of rock fragments in the water.

Abrasion is probably more intense in the surf zone than in any other environment.

Wave Refraction

Wave refraction is the bending of waves, and it plays an important part in the shoreline process.

Because of refraction, wave energy is concentrated against the sides and ends of headlands that project into the water, whereas wave action is weakened in bays.

Wave Refraction – Parallel to shore

Longshore Current

A longshore current is a near-shore current that flows parallel to the shore.

Turbulence allows longshore currents to easily move fine suspended sand and to roll larger sand and gravel particles along the bottom.

Longshore Currents

Erosional Features

Shoreline features that originate primarily from the work of erosion are called erosional features. Sediment that is transported along the shore and deposited in areas where energy is low produces depositional features.

Erosional Features

Wave-Cut Cliffs and Platforms Wave-cut cliffs result from the cutting action of the

surf against the base of coastal land. A flat, bench-like, wave-cut platform forms in front of the wave-cut cliff.

Sea Arches and Sea Stacks When two caves on opposite sides of a headland

unite, a sea arch results. Eventually, the arch falls in, leaving an isolated remnant, or sea stack, on the wave-cut platform.

Sea Arch and Sea Stack

Depositional Features

Where longshore currents and other surf zone currents are active, several features related to the movement of sediment along the shore may develop.

Spits, Bars, and Tombolos

A spit is an elongated ridge of sand that projects from the land into the mouth of an adjacent bay.

A baymouth bar is a sandbar that completely crosses a bay.

A tombolo is a ridge of sand that connects an island to the mainland or to another island.

Evolution of Shoreline Features

Barrier Islands

Barrier islands are narrow sandbars parallel to, but separate from, the coast at distances from 3 to 30 kilometers offshore.

Barrier Islands

Stabilizing the Shore

Protective Structures Groins, breakwaters, and seawalls are some

structures built to protect a coast from erosion or to prevent the movement of sand along a beach.

Beach nourishment Beach nourishment is the addition of large quantities

of sand to the beach system.

Stabilizing Structures

Groins are structures built at right angles to the shore to trap sand moving parallel to the shore to maintain beaches.

Seawalls are structures built parallel to shore that shields the coast from breaking waves.

Miami Beach Before and After Beach Nourishment

Coastlines & Seas Video 55 minYou will need to write 10 facts from the video.

Essential QuestionsYou have 15 minutes to answer the questions from this section. Be prepared to discuss your answers.

How does refraction affect wave action along the shore?Wave energy is concentrated against the sides of headlands, and it is weakened in the bays.

What do longshore currents do?Longshore currents move fine suspended sand and roll larger sand and gravel along the bottom and along the shore.

By which processes do shoreline features form?Waves erode, transport, and deposit sediment, forming many shoreline features.

What structures can be built to protect a shoreline?Groins, breakers, and seawalls are structures built to protect the shoreline.

What is beach nourishment?Beach nourishment is an approach to stabilize the shoreline by adding large quantities of sand to the beach system.