1. Movements of the Oceans
Chapter 21

2. Ocean Currents Ocean water moves in giant streams called CURRENTS.
Two categories: Surface & Deep Currents

3. Surface Currents
Created as Wind (moving air) pushes the water causing the water to move in the same direction as the air
Made to curve due to the Coriolis Effect - the tendency of a moving object to follow a curved path rather than a straight path because of the Earth’s rotation.
Northern Hemisphere – currents curve to the right, or clockwise
Southern Hemisphere – currents curve to the left, or counterclockwise
Creates GYRES – huge circles of moving water

4. Global Ocean Surface Currents
→Warm water currents → Cold water currents

5. Deep Currents Cold, dense currents far below the surface
Created as cold, dense water of the polar regions sinks and flows beneath warmer ocean water.
Density is affected by temperature
Cold water molecules contract creating denser water that sinks
Warm water molecules are farther apart and less dense causing them to rise above more dense water
Density is affected by salinity
Water with more dissolved solids is more dense and sinks
Arctic Bottom Water is -2˚C and has high salinity making it very dense

6. Antarctic Deep Current

7. Ocean Waves
Periodic up-and-down movement of water created as moving air pushes the water.
Crest – highest part
Trough – lowest part
Wave height – vertical
distance between crest
and trough
Wavelength – distance
from crest to crest
Wave period – time
required for 2 consecutive
waves to pass a given point

8. Water molecules move in a circular motion
Energy is transferred from water molecule to water molecule in the direction of the wave.
Water molecules move in a circular motion
At a depth of about ½ the wavelength there is almost no circular motion of water molecules.
Wave size is determined by 3 factors
Speed of the wind
Length of time the wind blows
Fetch – the distance the wind blows across open water

9. Height of the wave changes as the wave approaches the coast forming breakers
Breaking waves erode sediment from the ocean floor and move sediments along the coastline

10. Refraction – waves bend as they approach the coastline
Longshore current – flow parallel to the shore and carry large quantities of sand
Undertow – irregular current, occurring only near shorelines, created as water carried onto a beach is pulled back into deeper water by gravity.
Rip current – a fast moving current that flows perpendicular to the shore that forms when large
breakers return to the
ocean through channels
that cut through
underwater sandbars
running parallel to the
beach.

11. Tides
Periodic rise and fall in ocean levels caused by the gravitational pulls of the moon and sun.
Occurs every 24hours and 50min.
High tide – when water level is highest in an area
Low tide – when water level is lowest in an area
Tidal range – difference between high and low tides

12. Spring Tides Neap Tides
Sun Earth and Moon are in line (new moon and full moon)
Sun and Moon’s gravitational pull work together to increase the pull of the water and increases the tidal range
Produces higher high tides and lower low tides
Neap Tides
Sun Earth and Moon are at 90˚ angle (first-quarter and third-quarter moon)
Sun and Moon’s gravitation pull work against each other to reduce the pull of the water
Produces lower high tides and higher low tides.