Oceans

1. Oceans Mrs. Hutchcroft 6th Grade Science

2. Ocean Water • Oceans are important because they provide homes to many organisms • Oceans provide resources, such as food, salt, and transportation • Oceans provide water for precipitation • Oceans provide oxygen (70% of Earth’s oxygen!) produced by ocean organisms

3. Formation of Oceans • More than three billion years ago, oceans formed from volcanic water vapor that collected in the atmosphere and then fell as torrential rains

4. Composition of Ocean Water • Ocean water contains many dissolved substances, such as calcium, magnesium, and sodium that make it taste salty • Two most abundant elements in the dissolved salts are sodium and chloride ions, which combine to form a salt called halite • Salinity: a measure of the amount of solids, or salts, dissolved in seawater • Ocean water contains 35 grams dissolved substances per kilogram of water • Erupting volcanoes add elements such as sulfur and chlorine to ocean water

5. Composition of Ocean Water

6. Dissolved Gases • Gases enter the ocean from the atmosphere • Oxygen enters the ocean from the atmosphere and photosynthesis of ocean organisms • Carbon dioxide enters from the atmosphere and from respiration of ocean organisms; forms carbonic acid, which controls ocean acidity • Nitrogen provides nutrients for plants and is used in plant and animal tissues – most abundant dissolved gas

7. Water Temperature and Pressure • Both vary with depth • Three layers: • Warm surface layer: receives sun energy; warmest surface layer is near the equator • Thermocline: begins at a depth of about 200 m; temperatures rapidly drop with increasing depth • Deep-water layer – extremely cold

8. Water Layers

9. Water Temperature and Pressure • Pressure, or force per unity area, increases about 1atmosphere for every 10 meter increase in depth • For example: at a depth of 20 m, a scuba diver would experience a pressure of 3 atm (1 atm of air + 2 atm of water)

10. Ocean Currents and Climate

11. Ocean Currents and Climates • Mass movement or flow of ocean water • River within the ocean • Two types • Surface and Deep

12. Surface Currents: • Wind that moves only the upper few hundred meters of water • Gulf Stream-100 km wide current of warm water flowing east across the North Atlantic Ocean • Discovered in the 1500s by Ponce de Leon and his pilot Anton de Alaminos • Flows from Florida northeastward toward North Carolina where it curves toward the east and becomes slower and broader

13. Surface Currents Controlled by three factors • Global winds- Cause surface currents to flow in the direction the wind is blowing • Coriolis Effect • Continental Deflections Winds Driving Currents Trade Winds - Push equatorial currents westward Westerly Winds - Push polar currents eastward Winds Near India - Reverse directions between summer and winter producing monsoons

14. Coriolis Effect • The apparent curving of moving objects due to the Earth’s rotation • Northern Hemisphere = clockwise • Southern Hemisphere = counter clockwise • Western coasts currents – cold; prevent excessive summer warming • Eastern coasts currents – warm ; keep northern climates mild • Continental Deflections • Shape of continents change the direction of current flow

15. Deep/Density Currents • Stream like movement of ocean water far below surface; forms when more dense sea water sinks beneath less dense water • Density currents help regulate global rainfall patterns and temperatures • North of Iceland, a density current flows along the ocean floor toward the Atlantic Ocean and spreads into the Pacific and Indian Oceans; warm Gulf Stream water replaces this cold current • Decreasing the temperature of water increases density • Increasing the salinity of water increases density

17. Upwelling • The movement of deep, cold, nutrient rich water to the surface • Nutrients promote growth of fish and plants • Areas are important fishing grounds • Affects climate of coastal areas

19. Question 1 • What is a surface current and what causes them?

20. Answer • Surface currents move water horizontally – parallel to the Earth’s surface • They are powered by wind

21. Question 2 • What is the Coriolis Effect?

22. Answer • The Coriolis effect is the shifting of winds and surface currents caused by Earth’s rotation.

23. Question 3 • What is upwelling?

24. Answer • Upwelling is a vertical circulation in the ocean that brings deep, cold water to the ocean surface.

26. Waves Rhythmic movement that carries energy through water and is caused by: • Wind • Earthquakes • Gravitational force of the Moon and Sun.

27. Parts of a Wave • Crest – highest point of a wave • Trough – lowest point of a wave • Wave Height – vertical distance between the crest and the trough • Wavelength – horizontal distance between two crests or two troughs

28. Wavelength Crest Wave Height Still Water Trough Wave Parts

29. Wave Movement • When a wave passes through the ocean, individual water molecules move up and down but they do not move forward or backward unless the wave is breaking on shore.

30. Wave Movement • When a wave breaks against the shore, the crest outruns the trough and the crest collapses. • Called a breaker. • In this case, water does move forward and backward. • Wave Erosion – wears away both rocky shores and beaches

31. Waves Caused by Wind • When wind blows across a body of water, friction causes the water to move along with the wind. • Wave Height depends on – • Wind speed • Distance over which the wind blows • Length of time the wind blows

35. Tides • The rise and fall in sea level, caused by gravity from Earth, Moon, and Sun is called a tide. • Caused by a giant wave. • One low-tide/high-tide cycle takes about 12 hrs and 25 min. • Tidal range is the difference in ocean level between high-tide and low-tide

36. What is the Tidal Range? • HT = 30 ft, LT = 20 ft • HT = 20 ft, LT = 12 ft • HT = 50 ft, LT = 20 ft

37. Gravitational Effect of the Moon • Two big bulges of water form on the Earth: • one directly under the moon • another on the exact opposite side • As the Earth spins, the bulges follow the moon.

39. Gravitational Effect of the Sun • Spring Tides • Earth, Moon, and Sun are lined up • High Tides are higher and Low Tides are lower than normal

41. Gravitational Effect of the Sun • Neap Tides • Earth, Moon, and Sun form right angles • High Tides are lower and Low Tides are higher than normal

43. Life in the Oceans • Types of life are classified by WHERE organisms live in the ocean: • Plankton: tiny marine animals that float in the upper ocean layers (e.g. eggs of ocean animals, very young fish, larvae jellyfish and crabs, and tiny adults of some organisms) • Nekton: animals that swim rather than drift in the currents (e.g. fish, whales, shrimp, turtles, and squid) • Bottom dwellers: can burrow in sediments, walk or swim on the bottom, or be attached to the seafloor (e.g. anemones, crabs, corals, sea cucumbers, sea star, sponges)

44. Ocean Ecosystems • Community of organisms and nonliving factors such as sunlight, water, nutrients, sediment, and gases • Producers: organisms hat make their own food through photosynthesis or chemosynthesis • Consumers: eat producers to get energy • Decomposers: break down materials and release them back into the ecosystem • Energy is transferred from producers to consumers and decomposers through food chains and webs • Ocean nutrients are recycled through the ecosystem, particularly in coral reefs