Ch 16

1
Ch 16

• The Dynamic Ocean

2
Surface Circulation

• Surface Currents
• movements of water that flow horizontally near
  the surface
• develop from friction between the ocean and the
  wind

3
Surface Circulation

• Gyres
• huge circular-moving current systems that
  dominate the surfaces of the oceans.
• Coriolis effect
• deflection of currents away from their original
  course as a result of Earths rotation

4
Ocean Currents and Climate

• Currents from low-latitude regions moving into
  higher latitudes transfer heat from warmer to
  cooler areas
• Upwelling
• rise of cold water from deeper layers to replace
  warmer surface water
• brings greater concentrations of dissolved
  nutrients to the surface

5
Deep Ocean Circulation

• Density currents
• Vertical currents of ocean water that result from
  density differences among water masses
• Increases in seawater density can be caused by a
  decrease in temperature or an increase in salinity

6
Conveyor Belt Model

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

7
Waves

• Most ocean waves obtain their energy and motion
  from the wind.
• wave height - vertical distance between the
  trough and crest.
• Wavelength - horizontal distance between two
  successive crests or two successive troughs.
• wave period - time it takes one full wave to pass
  a fixed position.
• Fetch - distance that the wind has traveled
  across open water.

8
Tides

• Daily changes in the elevation of the ocean
  surface
• Result from the gravitational attraction exerted
  upon Earth by the moon

9
Tides

• Tidal range - difference in height between
  successive high and low tides
• Spring tides - have the greatest tidal range due
  to the alignment of the Earthmoonsun system
• Neap tides - have the lowest tidal range,
  occurring near the times of the first-quarter and
  third-quarter phases of the moon.

10
Forces Acting On The Shoreline

• Waves along the shoreline are constantly eroding,
  transporting, and depositing sediment.
• Wave Impact
• Abrasion - the sawing and grinding action of rock
  fragments in the water
• Wave Refraction - the bending of waves

11
Forces Acting On the Shoreline

• Wave Refraction
• 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.

12
Forces Acting On The Shoreline

• Longshore Current - 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.