Transcript Volcanoes and Igneous Activity Earth

Chapter 16
The Dynamic
Ocean
Section 16.1
Ocean Circulation
16.1 The Composition of Seawater
Surface Circulation
 Ocean current is the mass of ocean water
that flows from one place to another.
 Surface Currents
• 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
16.1 The Composition of Seawater
Surface Circulation
 Gyres
• 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.
16.1 The Composition of Seawater
Surface Circulation
 Ocean Currents and 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
What causes ocean surface
currents?
A. Gravitational attraction
B. Friction between the ocean and wind
on its surface
C. Ocean movements associated with
earthquakes
D. Changes in water density
Currents affect climate by
A. Making ocean water evaporate
B. Transferring heat and cold between
the tropics and polar regions
C. Changing the density of water in the
tropics
D. Transferring heat from the polar
regions to the tropics
16.1 The Composition of Seawater
Surface Circulation
 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
16.1 The Composition of Seawater
Deep-Ocean Circulation
 Density Currents
• 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.
What is the importance of
upwelling?
A. It brings warm water from the tropics
to the poles.
B. It decreases winds along exposed
coastlines.
C. It helps warm the North Atlantic gyre.
D. It brings dissolved nutrients to the
ocean’s surface.
A decrease in seawater
temperature or an increase in
salinity causes
A. Upwelling along tropical coast.
B. An increase in seawater density.
C. The circulation of ocean gyres.
D. A decrease in seawater density.
16.1 The Composition of Seawater
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.
• Example: The Mediterranean Sea
16.1 The Composition of Seawater
Deep-Ocean Circulation
 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.
Conveyor Belt Model
Cross Section of the Arctic Ocean
What causes density currents to
form in the Mediterranean Sea?
A. Freezing
B. Evaporation
C. Melting Ice
D. Upwelling