Ocean Circulation

1. Ocean Circulation Ch. 16.1

2. Currents move water from place to place

3. There are 2 kinds of currents…

4. First kind of current: • Surface currents: move on or near surface of ocean • Most are caused by wind • Friction between wind blown air and the water surface causes the water to move • Controlled by wind belts, earth’s rotational effect and location of continents

5. Surface Currents Gyres: huge circular-moving current systems that dominate the surface of the oceans • Five main ocean gyres: • North Pacific Gyre • South Pacific Gyre • North Atlantic Gyre • South Atlantic Gyre • Indian Ocean Gyre

6. Gyres

7. Surface Currents Other factors also influence the movement of ocean waters: • Coriolis Effect- deflection of currents away from their original course as a result of Earth’s rotation • Because of Earth’s rotation, currents are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

8. Surface Currents Other factors also influence the movement of ocean waters: • Coriolis Effect- deflection of currents away from their original course as a result of Earth’s rotation • Because of Earth’s rotation, currents are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

12. Surface Currents 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 or adjacent land areas. • Ocean water movement accounts for about a quarter of this heat transport. Winds transport the remaining three-quarters.

14. Surface Currents

15. What direction do most currents NORTH of the equator move?

16. CLOCKWISE!

17. What direction do most currents SOUTH of the equator move?

18. COUNTERCLOCKWISE!

19. Western side of ocean has warm currents traveling from equator • Eastern side of ocean has cool currents moving toward equator

20. Examples of warm water currents: • Gulf Stream • Brazil • Kuroshio

21. Examples of cold water currents: • California current • Canary current • Labrador current

22. Surface Currents Upwelling: • In addition to producing surface currents, winds can also cause vertical water movements. • Upwelling is the rising 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.

23. Second kind of current: 2. Deep density currents: cold, dense currents that flow very slowly beneath surface of ocean • Occurs when denser seawater moves towards an area of less dense seawater

24. In the deep ocean, denser water around the Poles sinks and travels along the ocean floor toward the equator. • At the same time, less dense water at the equator rises and moves towards the poles along the surface.

25. Evaporation also plays a role within deep ocean currents. Density currents result from increased salinity of ocean water due to evaporation (leaving more dissolved salts behind). • These events form a continuous cycle (conveyor belt) that circulate ocean water.

26. Salinity, Density and Ocean Circulation Demonstration! Please write your observations on the same sheet as your bellringer.

27. Salinity & Deep Ocean Currents • Is salt water heavier or lighter (higher or lower in density) than freshwater? Make sure that you explain your answer in terms of the results that you obtained from the experiment. • If evaporation causes surface water to be salty, where would you expect ocean water to be very dense? • Does this correspond to where deep ocean currents originate? If not, can you explain why? • Does the density of ocean water have any relationship to the temperature of ocean water? If yes, please explain.

28. Salinity & Deep Ocean Currents • In Earth's equatorial regions, surface ocean water becomes saltier as the water, but not the salt, evaporates. However, the water is still warm enough to keep it from sinking. Water that flows towards the poles begins to cool. • In a few regions, especially in the North Atlantic, cold salty water can sink to the sea floor. It travels in the deep ocean back towards the equatorial regions and rises to replace water which is moving away at the surface. • This whole cycle is very important in regulating climate as it transports heat from the equatorial regions to polar regions of Earth. The full cycle can take a thousand years to complete.

29. Wave Generating forces • WIND • TIDES • Sometimes Earthquakes

30. Features of a wave CREST WAVE HEIGHT TROUGH WAVELENGTH

31. Wavelength • Distance from one crest to another

32. Wave Height • Difference between crest to trough

34. Period: • The time it takes one wavelength to pass a given point

35. Speed= wavelength period

36. Test your knowledge… What is the speed of a wave 24 meters long with a period of 4 seconds?

37. Speed = 24 meters= 6 meters/sec 4 sec

38. Observe an animation of wave motion.

39. Swells • Group of long, rolling waves all about the same size • Come at regular intervals

41. Height of wind-formed waves depends on 3 things… • Length of time the wind blows • Speed of wind • FETCH: length of open water over which the wind blows in a single direction

43. As waves approach shore, the water is so shallow that they touch bottom. This happens at a depth of one-half the wavelength. As the wave scrapes bottom, the lower part of wave slows down and upper par moves ahead. The crest falls over and breaks onto the beach.

45. Observe waves as they break on the shore.

48. MAVERICKS

50. Waves and the shore: • Breakers – foamy mass of water that washes onto shore • Undertow • Long shore current • Tsunamis • Rip current – strong surface currents that flow away from the beach; hazard to swimmers