The Movement of Ocean Water

1. The Movement of Ocean Water Chapter 20

2. Sections • Currents • Waves • Tides

3. Currents • Ocean currents are streamlike movements of water. • When these movements occur at or near the surface of the ocean, they are called surface currents.

4. Currents • Winds blowing across the Earth’s surface create surface currents in the ocean. • Near the equator, they flow east to west. But near the poles, they flow west to east.

5. Currents • Earth’s rotation causes surface currents to move along curved paths in stead of straight lines. • This is known as the Coriolis effect.

6. Currents • Continents also cause the surface currents to deflect, or change direction.

7. Currents • Surface currents are also affected by the temperature of the water in which they form. • Warm-water currents carry warm water to other parts of the ocean … and cool-water currents carry cool water.

9. Currents • The temperature of surface currents affect the climate of land near the area where they flow.

10. Currents • Upwelling is when cold, nutrient-rich water from the deep ocean rises to the surface and replaces warm surface water. • The change in location of warm and cool water in the Pacific is known as El Nino.

11. Currents • Deep currents are streamlike movements of ocean water far below the surface. • These currents form in parts of the ocean where water density increases.

12. Currents • Lower temperatures and higher salinity cause ocean water to become more dense. • Formation of ice and evaporation raise the salinity of water.

13. Waves • Most waves form as the wind blows across the water’s surface and transfers energy to the water. • As the energy moves through the water – so do the waves.

14. Waves • Crest is the highest point. • Trough is the lowest point. • Wavelength is the distance between two crests or troughs. • Wave height is the vertical distance between crest and trough.

16. Waves • Wave period is the time between the passage of two wave crests (or troughs) at a fixed point. = wavelength (m) wave speed (m/s) wave period (s)

17. Waves • As waves approach the shore, they increase in height and eventually crash as breakers. • Water moves back to the ocean under the waves in a current called an undertow. • Waves hitting the shore at an angle cause a current along the shoreline called a longshore current.

18. Waves • There are two types of waves in the open ocean: • Whitecaps break in the open ocean before they get close to shore. • Swells are rolling waves that move steadily across the ocean.

20. Waves • Tsunamis are waves that form when a large volume of ocean water is suddenly moved up or down. • They can be caused by earthquakes, volcanic eruptions, landslides, underwater explosions, or the impact of a meteor or comet. • The highest recorded was 64m high!

25. Waves • A storm surge is a local rise in sea level near the shore that is caused mainly by strong winds from a storm, such as a hurricane.

26. Tides • Tides are daily changes in the level of ocean water. • The moon’s pull is strongest on the part of the Earth directly facing the moon. • Water on the opposite side of Earth bulges because of the rotation of the Earth.

27. Tides • When the ocean bulges – it is called a high tide. • Water is drawn away from the area between the high tides – causing a low tide. • The moon revolves around the Earth more slowly than the Earth turns – so high tide is at a different time every day.

28. Tides • Lunar phases or the changes in the moon’s appearance, are connected to the tides. • The lunar cycle of these changes lasts about 28 days. • The sun also affects tides, but is less powerful than the moon because of its distance from Earth.

29. Tides • Tides with the largest range are called spring tides and happen when the sun, Earth, and moon line up with one another. • Spring tides occur with every new and full moon, about every 14 days. • Tides with the smallest range are called neap tides and happen when the sun, Earth, and moon for a 90° angle.