1. Physical Oceanography

2. I. The Oceans Objectives Identify methods used by scientists to study Earth ’ s oceans. Discuss the origin and composition of the oceans. Describe the distribution of oceans and major seas.

3. Origin of the Oceans Where did the water come from? Comets – Scientists hypothesize that Earth ’ s water could have originated from two sources. Comets occasionally collide with Earth and release water (about 0.5% water) on impact–possibly enough to have filled the ocean basins over geologic time.

4. Origin of the Oceans Where did they come from? Volcanism – Shortly after the formation of Earth, violent volcanism released huge amounts of water vapor, carbon dioxide, and other gases, which combined to form Earth ’ s early atmosphere. – As Earth ’ s crust cooled, the water vapor gradually condensed into oceans.

5. Oceanography In the 1920s, sonar (sound navigation and ranging) was first used to determine water depth. Sound waves are now used to map the ocean floor.

6. Distribution of Earth ’ s Water The oceans contain 97 percent of the water found on Earth. The remaining 3 percent is freshwater located in the frozen ice caps of Greenland and Antarctica and in rivers, lakes, and underground sources.

7. Distribution of Earth ’ s Water – Sea level has risen and fallen by hundreds of meters in response to melting ice during warm periods and expanding glaciers during ice ages. – Tectonic forces that lift or lower portions of the seafloor has also affected sea level.

8. Sea Level (nivel del mar) The level of the oceans ’ surfaces

9. Distribution of Earth ’ s Water The Blue Planet – Approximately 71 percent of Earth ’ s surface is covered by oceans that have an average depth of 3800 m. – Because most landmasses are in the northern hemisphere, oceans only cover 61 percent of the surface. – Water covers 81 percent of the southern hemisphere.

10. Seawater: Objectives Compare and contrast the physical and chemical properties of seawater. Explain ocean layering. Describe the formation of deep-water masses. – salinity – temperature profile – thermocline Vocabulary

11. What is Ocean Water Made of? Seawater is a solution of about 96.5 percent water and 3.5 percent dissolved salts. The most abundant salt in seawater is sodium chloride (NaCl). Most elements on Earth are present in seawater.

12. Chemical Properties of Seawater: Salinity The total salt content of seawater is, on average, 35 ppt, or 3.5 percent. Seawater also contains dissolved gases and nutrients.

13. Processes that Affect Salinity Processes that decrease salinity – Precipitation – Sea ice melting – Icebergs melting – Runoff from land Processes that increase salinity – Evaporation – Formation of sea ice

14. Chemical Properties of Seawater: Salinity

15. Salinity (salinidad) A measure of the amount of dissolved salts

16. Physical Properties of Seawater: Density Freshwater has a maximum density of 1.00 g/cm 3. Seawater is denser than freshwater because salt ions are heavier than water molecules. Salt water freezes at a lower temperature than fresh water because the salt interferes with the bonds.

17. Ocean Layering: Temperature The ocean’s surface water temperature varies with the amount of solar radiation received, which is primarily a function of latitude.

18. Physical Properties of Seawater: Absorption of Light – Water absorbs light, which gives rise to another physical property of oceans—they are dark. – In general, light penetrates only the upper 100 m of seawater. – Red light penetrates less than blue light. – Light sufficient for photosynthesis exists only in the top 100 m of the ocean.

19. Ocean Layering: Temperature A typical ocean temperature profile plots changing water temperatures with depth. Ocean water temperatures decrease significantly with depth.

20. Ocean Layering: Temperature Based on temperature variations, which causes differences in density, the ocean can be divided into three layers. – The first layer is a relatively warm, sunlit, surface layer some 100 m thick. – The thermocline is a transitional layer which is characterized by rapidly decreasing temperatures with depth. – The bottom layer is cold and dark with temperatures near freezing.

22. Thermocline (termoclina) A transitional layer which is characterized by rapidly decreasing temperatures with depth

23. The Yellow Sea Its name comes from the sand particles from Gobi Desert sand storms that turn the surface of the water golden yellow.

24. The White Sea

25. Question? What happens to a white hat that falls in the red sea?

26. Water Masses Cold water migrates toward the equator as a cold, deep water mass along the ocean floor. – To start, sea ice that forms in the polar regions does not incorporate salt ions into growing ice crystals, causing them to accumulate beneath the ice. – As the cold water beneath the ice becomes saltier and denser than the surrounding seawater, it sinks. – Surface currents in the ocean also bring relatively salty midlatitude or subtropical waters into polar regions where they cool and sink. – The dense, salty water then migrates toward the equator as a cold, deep water mass along the ocean floor.

27. Water Masses Three water masses account for most of the deep water in the Atlantic Ocean. 1.Antarctic Bottom Water forms when antarctic seas freeze during the winter and water temperature drops below 0°C. 2.North Atlantic Deep Water forms in a similar manner offshore from Greenland. 3.Antarctic Intermediate Water forms when the relatively salty waters of the Antarctic Ocean decrease in temperature during winter and sink.

28. Water Masses The Indian and Pacific Oceans contain only the two deep antarctic water masses.

29. – wave – crest – trough – breaker Objectives Describe the physical properties of waves. Explain how tides form. Compare and contrast various ocean currents. Vocabulary Ocean Movements – tide – density current – surface current – upwelling

30. Ocean Movements A wave is a rhythmic movement that carries energy through space or matter, such as ocean water. Ocean Movements As an ocean wave passes, the water moves up and down in a circular pattern and returns to its original position.

31. Wave Characteristics A crest is the highest point of a wave. Ocean Movements A trough is the lowest point of a wave. The vertical distance between crest and trough is the wave height; the horizontal crest-to-crest distance is the wavelength.

32. Wave Characteristics The wavelength determines the wave base, which is the depth to which the wave disturbs the water. Ocean Movements Wave speed increases with wavelength.

33. Wave Characteristics Ocean Movements

34. Wave Characteristics Wave Height Ocean Movements – Wave heights depend upon three factors: wind speed, wind duration, and fetch. – Fetch refers to the expanse of water that the wind blows across. – Large storm waves can be much higher than average.

35. Wave Characteristics Breaking Waves Ocean Movements – Ocean waves begin to lose energy and slow down near the shore because of friction with the ocean bottom. – As the water becomes shallower, incoming wave crests gradually catch up with the slower wave crests ahead. – Breakers are waves where the crests collapse forward when the wave becomes higher, steeper, and unstable as it nears shore.

36. Wave Characteristics Breaking Waves Ocean Movements

37. Tides Tides are the periodic rise and fall of sea level. Ocean Movements The highest level to which water rises is known as high tide, and the lowest level is called low tide. Because of differences in topography and latitude, the tidal range—the difference between high tide and low tide—varies from place to place. Generally, a daily cycle of high and low tides takes 24 hours and 50 minutes.

38. Tides Ocean Movements Differences in topography and latitude cause three different daily tide cycles. Areas with semidiurnal cycles experience two high tides per day. Areas with mixed cycles have one pronounced and one smaller tide each day. Areas with diurnal cycles have one high tide per day.

39. Causes of Tides The basic causes of tides are the gravitational attraction among Earth, the Moon and the Sun, as well as the fact that gravitational attraction decreases with distance. Ocean Movements Both Earth and the Moon orbit around a common center of gravity. As a result, Earth and the Moon experience gravitational and centrifugal forces that generate tidal bulges on opposite sides of Earth.

40. Causes of Tides Ocean Movements

41. Causes of Tides The Sun ’ s Influence Ocean Movements – The gravitational attraction of the Sun and Earth ’ s orbital motion around the Sun also generate tides. – Lunar tides are more than twice as high as those caused by the Sun because the Moon is much closer to Earth. – Solar tides can either enhance or diminish lunar tides. Spring tides occur when the Sun, the Moon, and Earth are aligned, causing high tides to be higher than normal and low tides to be lower than normal. During neap tides, high tides are lower and low tides are higher than normal.

42. Causes of Tides The Sun ’ s Influence Ocean Movements

43. Ocean Currents A density current moves slowly in the deep ocean and is caused by differences in the temperature and salinity of ocean water, which in turn affect density. Ocean Movements Surface currents are wind-driven currents that affect mainly the upper few hundred meters of the ocean and can move as fast as 100 km per day. Surface currents follow predictable patterns influenced by Earth ’ s global wind systems.

44. Ocean Currents Gyres Ocean Movements – The continents deflect ocean currents to the north and south causing closed circular current systems, called gyres, to develop. – There are five major gyres: the North Pacific, the North Atlantic, the South Pacific, the South Atlantic, and the Indian Ocean. – The parts of all gyres closest to the equator move towards the west as equatorial currents until they are deflected toward the poles by a landmass. – After cooling in the polar regions, the current, deflected by landmasses, moves back toward the equator.

45. Ocean Currents Ocean Movements

46. Upwelling Upwelling is the upward motion of ocean water. Ocean Movements Areas of upwelling exist mainly off the western coasts of continents in the trade-wind belts. Upwelling waters are rich in nutrients, which support abundant populations of marine life.

47. Upwelling Ocean Movements