Surface ocean currents are driven by wind and develop circular gyre patterns. They transfer heat between latitudes and influence climate. Upwelling brings nutrients to surface waters. Deep currents are driven by density differences from temperature and salinity changes. The global conveyor belt model depicts a circulation pattern from the Atlantic to the Pacific and back. Waves are characterized by height, wavelength, period, and fetch. Breaking waves increase in height and decrease in wavelength near shore. Tides have spring and neap variations due to lunar phases. Shoreline processes include abrasion, refraction, and longshore transport, which shape features like barrier islands.
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55 The DynamicOcean
Reporters:
Karl Bryan Quitiol
Jan Christopher Co
2.
Surface Circulation
Oceancurrent 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.
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.
5.
Surface Circulation
OceanCurrents 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.
6.
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.
7.
Deep-Ocean Circulation
DensityCurrents
• 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.
8.
Deep-Ocean Circulation
HighLatitudes
• 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.
9.
Deep-Ocean Circulation
AConveyor 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.
Waves
Wave Characteristics
Wavesand Tides
• 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.
12.
Waves
Wave Characteristics
•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.
Waves
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.
Tides
Tide Cycle
•Spring tides are tides that have the greatest
tidal range due to the alignment of the Earth–
moon–sun system.
• Tidal range is the difference in height between
successive high and low tides.
• 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.
Forces Acting onthe Shoreline
Wave Impact
Shoreline Processes and Features
• 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
• 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.
19.
Forces Acting onthe Shoreline
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.
Forces Acting onthe Shoreline
Longshore Transport
Shoreline Processes and Features
• 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.
Depositional Features
BarrierIslands
• Barrier islands are narrow sandbars parallel to,
but separate from, the coast at distances from 3
to 30 kilometers offshore.