Chapter 10 Ocean Currents and Gyres

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What factor contributes to the formation of ocean waves by transferring energy from the air to the water?

Temperature difference

Pressure gradient

Humidity level

Wind speed (correct)

What determines the final size of ocean waves, beyond which they are no longer sustainable and form whitecaps?

Wave height at the shore

Changes in water temperature

Maximum fetch and duration for a given wind velocity (correct)

Wind direction

What happens to the waves generated when the wind stops or changes direction?

They continue to grow larger indefinitely

They quickly transform into tsunamis

They maintain the same size

They lose energy and dissipate (correct)

What term is used for ocean waves that are lower in height, longer in length, and carry the wind's original energy to the shore?

Swells Signup and view all the answers

What kind of motion do ocean waves exhibit that allows the waveform to move forward while the water particles move in a circular path?

Circular orbital motion Signup and view all the answers

What term is used for the state of ocean waves where the energy lost from whitecapping equals the energy gained from the wind's velocity?

Fully developed seas Signup and view all the answers

In the process of wave formation, what role does the length of time the wind blows play?

Affects wave size Signup and view all the answers

What factor helps in the transfer of energy from the air to the water in the creation of ocean waves?

Fetch (distance traveled by wind across the open ocean) Signup and view all the answers

What happens to the density of seawater in high latitude areas when seawater freezes into sea ice?

It increases because the salt does not become part of the ice Signup and view all the answers

What creates the highest-density water in the world near Antarctica?

The generation of Antarctic bottom water Signup and view all the answers

What are some natural processes that can modify coastlines?

Stream erosion Signup and view all the answers

Which factor provides most of the energy that modifies shorelines?

Wind-generated waves Signup and view all the answers

What is the role of wave crests in ocean waves?

They are the highest part of the wave above the average water line Signup and view all the answers

What causes large waves to crash along a shoreline on windless days?

Energy originating thousands of miles away Signup and view all the answers

What is the primary source of energy that impacts shorelines?

Wind-generated waves Signup and view all the answers

Where does thermohaline circulation begin?

High latitude areas Signup and view all the answers

What is the interface where shoreline, air, land, and sea meet called?

Dynamic shoreline Signup and view all the answers

How do humans impact shorelines?

By overdevelopment and unsustainable resource use Signup and view all the answers

Why does the west coast of the United States experience deformation and uplift?

Because it is the leading edge of the North American plate Signup and view all the answers

What is the primary reason for shoreline erosion problems along the Pacific Coast?

The sporadic nature of storms Signup and view all the answers

Why are many shorelines complex and difficult to understand?

Because of the multitude of factors affecting shoreline development Signup and view all the answers

What is an emergent coast?

A coast that has experienced uplift Signup and view all the answers

What is the primary cause of tides?

Gravitational attraction between the Earth, moon, and sun Signup and view all the answers

Why are barrier islands prone to extensive modification during storms?

Because they absorb a good portion of a storm's energy Signup and view all the answers

What is a common characteristic of the Atlantic and Gulf Coast shorelines?

Barrier islands Signup and view all the answers

What is an example of a submerged coast?

Drowned river mouths on the east coast of the U.S. Signup and view all the answers

In which season is wave activity generally light?

Summer Signup and view all the answers

What happens to sediment when wave activity is high?

Sediment washes away from the beach face Signup and view all the answers

What is the role of wave refraction in sediment movement along the shoreline?

Affecting the wave energy distribution along the shore Signup and view all the answers

What happens when waves approach the shore at an angle?

Wave energy is concentrated on headlands and diminishes in bays Signup and view all the answers

What is the result of significant backwash due to high wave activity?

Loss of sediment from the beach face Signup and view all the answers

How does wave refraction influence erosion and deposition along the shoreline?

Causes erosion in bays and deposition in headlands Signup and view all the answers

What is the impact of a net loss of sediment from a beach face?

Increased shoreline stability Signup and view all the answers

How does wave activity affect the movement of sediment along the shoreline?

Determines the net gain or loss of sediment Signup and view all the answers

What is the primary source of energy for generating ocean currents?

Transfer of energy from the wind to the water Signup and view all the answers

What is the name given to the large, circular-moving surface currents located within each ocean basin?

Gyres Signup and view all the answers

At approximately what latitude are the centers of the subtropical gyres located?

30° north or south latitude Signup and view all the answers

What is the term given to the deflection of free-flowing objects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere?

Coriolis Effect Signup and view all the answers

How many years does it take for the North Pacific Gyre to complete its current?

6 years Signup and view all the answers

Which of the following currents is not part of the North Pacific Gyre?

Gulf Stream Signup and view all the answers

What is the primary factor that influences the shape and direction of ocean currents?

Global pattern of prevailing winds Signup and view all the answers

How many main gyres are there in the world's oceans?

5 Signup and view all the answers

What is the diameter of the circular orbits at the ocean's surface equal to?

The wave height Signup and view all the answers

At what depth does the circular orbit become negligible?

½ the wavelength Signup and view all the answers

What happens to the wave as it approaches the shore?

The wave begins to feel the bottom Signup and view all the answers

What is the term for the turbulent water created by breaking waves?

Surf Signup and view all the answers

What is the scientific definition of a beach?

An accumulation of sediment along the landward edge of an ocean, marginal sea, or lake Signup and view all the answers

What is the approximate time it takes for the North Atlantic Gyre to complete its current?

3 years Signup and view all the answers

Which current is the only one that encircles the Earth?

West Wind Drift Signup and view all the answers

What is a common composition of beaches near volcanic islands?

Green or black minerals weathered from basaltic lava Signup and view all the answers

What is the primary cause of wave erosion during calm weather?

There is no erosion during calm weather Signup and view all the answers

What is the main factor that influences the Indian Ocean circulation?

Monsoons Signup and view all the answers

What is the force exerted by waves on the Atlantic Coast in the winter?

2,000 lbs per square foot Signup and view all the answers

What is the primary purpose of ocean surface circulation?

To moderate regional climates Signup and view all the answers

What is the process that occurs when the air expands rapidly in the cracks of rocks?

Wave impact forces Signup and view all the answers

Which type of currents warm the regions they flow near?

Poleward-moving currents Signup and view all the answers

What type of shorelines are more easily eroded?

Those composed of loose, unconsolidated sediment Signup and view all the answers

What is the result of the California Current on the climate of Southern California?

It decreases the temperature by 11°F Signup and view all the answers

What is the effect of the cool Peru Current on the climate of coastal Peru and Chile?

It lowers the humidity and precipitation Signup and view all the answers

What is the primary mechanism of deep-ocean circulation?

Density differences Signup and view all the answers

What is the result of upwelling on the surface water temperature?

It decreases the temperature Signup and view all the answers

What is the primary effect of upwelling on marine ecosystems?

It increases the concentration of dissolved nutrients Signup and view all the answers

What is the primary reason for the formation of wave-cut cliffs?

The concentration of wave energy on headlands Signup and view all the answers

What is the term for the zigzag pattern of sediment movement along the beach face?

Beach drift Signup and view all the answers

Which type of shoreline feature is formed from the erosion of rock and sediment?

Erosional feature Signup and view all the answers

What is the term for the current that flows parallel to the shore within the surf zone?

Longshore current Signup and view all the answers

What is the term for a ridge of sediment that extends from land into deeper water near the mouth of a bay?

Spit Signup and view all the answers

What is the term for a low ridge of sand that parallels the coast at distances from 2 to 20 miles offshore?

Barrier island Signup and view all the answers

What is the term for a sea cave that has eroded through to the opposite side of the headland, forming an arch?

Sea arch Signup and view all the answers

What is the primary reason for the formation of a marine terrace?

Uplift of the coast Signup and view all the answers

What is the direction of longshore currents along the east and west coasts of the U.S.?

Southward Signup and view all the answers

What is the term for a ridge of sand that connects an island or sea stack to the mainland?

Tombolo Signup and view all the answers

Why do most places experience two high tides and two low tides each day?

The Earth rotates much faster than the Moon Signup and view all the answers

What is the reason for the 50-minute delay in tidal cycles each day?

The lunar bulge's migration Signup and view all the answers

What is the primary factor that determines the magnitude of tidal ranges?

The alignment of the Earth, Moon, and Sun Signup and view all the answers

What type of tidal pattern is characterized by a single high tide and a single low tide each lunar day?

Diurnal tidal pattern Signup and view all the answers

What is the term used to describe the horizontal flow of water associated with the rise and fall of the tide?

Tidal current Signup and view all the answers

What is the term used to describe periods of little or no current during tidal cycles?

Slack water Signup and view all the answers

What is the result of the linear alignment of the Earth, Moon, and Sun during spring tides?

A larger tidal range Signup and view all the answers

What is the approximate percentage of the Sun's tide-generating effect compared to the Moon's?

46% Signup and view all the answers

How many variables must be precisely evaluated to predict the tides?

400 Signup and view all the answers

What is the term used to describe the areas affected by tidal currents?

Tidal flats Signup and view all the answers

What happens to a shoreline that remains stable for an extended period of time?

Erosion and deposition make it very straight and regular. Signup and view all the answers

Why does shoreline erosion pose a significant threat to human life and property?

It can occur quickly and have significant impact. Signup and view all the answers

What is the primary purpose of breakwaters?

To protect boats from the force of large breaking waves. Signup and view all the answers

What is a common environmental impact of beach nourishment?

Damage to coral ecosystems. Signup and view all the answers

What is the primary advantage of beach nourishment?

It is a cost-effective, long-term solution. Signup and view all the answers

What is the purpose of jetties?

To protect a coast from erosion at entrances to shipping areas. Signup and view all the answers

Why do coastal scientists and urban planners recommend relocation?

To allow nature to reclaim the beach and reduce storm damage. Signup and view all the answers

What is a factor that affects the rate of shoreline erosion?

The degree of tectonic activity. Signup and view all the answers

What is the term for structures built to protect a coast from erosion or prevent the movement of sediment?

Hard stabilization. Signup and view all the answers

Why is shoreline erosion a significant concern compared to other natural hazards?

It occurs quickly and has a significant impact on human life and property. Signup and view all the answers

Study Notes

The Ocean's Surface Circulation

Ocean currents are generated by the transfer of energy from wind to water.
Major surface currents are closely related to global patterns of prevailing winds.
The distribution of landmasses and the Coriolis Effect also influence surface currents.
Large, circular-moving surface currents (gyres) are located within each ocean basin.
There are 5 main gyres: North Pacific, South Pacific, North Atlantic, South Atlantic, and Indian Ocean.
The center of each gyre is located at approximately 30° north or south latitude, referred to as subtropical gyres.

Coriolis Effect

Due to Earth's eastward rotation, free-flowing objects are deflected to the right of their apparent direction in the Northern Hemisphere and to the left in the Southern Hemisphere.
This deflection is termed the Coriolis Effect.

Ocean Gyres

North Pacific Gyre: consists of North Equatorial Current, Kuroshio Current, North Pacific Current, and California Current; takes approximately 6 years to complete.
North Atlantic Gyre: consists of North Equatorial Current, Gulf Stream, North Atlantic Current, and Canary Current; takes approximately 3 years to complete.
Large gyres develop a central area with no well-defined currents, such as the Sargasso Sea in the North Atlantic.
South Pacific Gyre: consists of South Equatorial Current, East Australian Current, West Wind Drift, and Peru Current.
South Atlantic Gyre: consists of South Equatorial Current, Brazil Current, West Wind Drift, and Benguela Current.
Indian Ocean Gyre: consists of South Equatorial Current, Agulhas Current, West Wind Drift, and West Australian Current; influenced by monsoons.

Surface Currents and Climate

Surface currents have a pronounced influence on climate.
Ocean water accounts for ¼ of the total heat transport, while winds account for the remaining ¾.
Poleward-moving warm currents warm the regions they flow near, such as the Gulf Stream and East Australian Current.
Equatorial-moving cool currents cool the regions they flow near, such as the Canary Current and Peru Current.
The California Current lowers temperatures in Southern California by nearly 11° F compared to the same latitudes on the US East Coast.

Upwelling and Deep-Ocean Circulation

Surface currents generate vertical movements of water (upwelling and downwelling).
Upwelling is the rising of cold water from deeper water to replace warmer surface water.
Coastal upwelling occurs in regions when winds blow parallel to the coast and toward the equator.
Upwelling brings higher concentrations of dissolved nutrients to the surface, promoting primary productivity.
Deep-ocean circulation is responsible for the mixing of seawater, with a significant vertical component due to density differences.
Thermohaline circulation begins in high-latitude areas where cold seawater freezes into sea ice, increasing the salinity and density of the surrounding water.

The Shoreline: A Dynamic Interface

Shorelines are dynamic locations that vary in topography, geology, and climate.
Shorelines are the transition zone of sediment deposition between the marine and continental environments.
The shore is the interface of the air, land, and sea.
Wave activity continually changes the shoreline, with some changes occurring rapidly and others slowly.
Human activities, such as overdevelopment and unsustainable resource use, can also impact shorelines.

Ocean Waves

Ocean waves are energy traveling along the interface between seawater and the atmosphere.
Wave characteristics include wave height, wavelength, and wave period.
The height, length, and period of a wave are dependent on wind speed, duration, and fetch.
As waves approach the shore, the water becomes shallower, and the waves begin to "feel" the bottom.
Waves eventually break, creating turbulent water (surf) and a turbulent sheet of water moving up the beach slope (swash).

Beaches and Shoreline Processes

Beaches are accumulations of sediment along the landward edge of an ocean, marginal sea, or lake.
Beaches are composed of material that is locally available.
Beach material can come from erosion of beach cliffs or coastal mountains, or from rivers.
Some beaches have a large biological component, such as shells and coral.
Beaches are constantly moving along the shoreline due to wave activity.
Wave erosion can be caused by pressure, wave impact forces, and abrasion.
Breaking waves can cause sediment to move toward and away from the shoreline.
Wave refraction (the slowing and bending of waves in shallow water) plays an important role in the distribution of wave energy along the shore.Here are the study notes for the text: