Earth’s Oceans

1. Earth’s Oceans

2. Ocean Water: Salinity - Key Points • Salinity is the amount of dissolved substances/ salts in the oceans • It is expressed in ‰, parts per thousand • Salinity, temperature, and density vary within the ocean • Salinity and temperature affect the density of water • Increased salinity and decreased temperature result in more dense water • 35 parts per thousand (ppt) or 3.5%

3. Ocean Water: Salinity • Salinity is the amount of dissolved solid material in water (more commonly thought of as salt) • The most common salt in seawater is sodium chloride • Because the proportion of the dissolved substances is such a small number, oceanographers express salinity in parts per thousand, ‰ • Where do you think these salts come from?

4. Ocean Water: Salinity • The main source of these salts in seawater is chemical weathering of rocks on the continents • They reach the ocean through runoff • The other major source is the earth’s interior

5. Ocean Water: Salinity • The salinity of ocean water varies slightly around the world • What can differences in salinity do? • In general, when the amount of water in the oceans changes, the salinity changes • Anything that increases the amount of water will decrease salinity (make the water more dilute) • Anything that decreases the amount of water will increase salinity • Brainstorm: what are some processes that could increase the water in oceans? Decrease the amount of water?

6. Objectives • Salinity and temperature affect the density of water • Increased salinity and decreased temperature result in more dense water • Scientists divide the ocean into zones of marine life based on sunlight, distance from the shore, and depth of the water

7. Ocean Water: Salinity • Salinity and Density • Recap: What is density? What is its formula? • The two main factors that affect density are salinity and temperature • The higher the salinity, the more dense the water

8. Ocean Water: Temperature and Density • Just like salinity, the temperature of the ocean varies • At the surface of the ocean, temperature differences are mostly due to the amount of energy received from the sun • This means: • Areas at lower latitudes (closer to the equator) receive more direct, and intense sunlight and are therefore warmer

9. Ocean Water: Temperature and Density • Temperature varies with depth • In most places, the water temperature decreases as you go deeper (this isn’t as true near the poles) • Temperature does not decrease evenly • Thermocline: area of rapid change in temperature (thermo= heat, cline = slope) • Important because it creates a vertical barrier between types of marine life

10. Ocean Water: Temperature and Density • Ocean water is layered based on differences in density Surface/Mixed Layer Thermocline/transition Layer Bottom/Deep Layer

11. Ocean Water: Temperature and Density • Surface/Mixed Layer • Water is the warmest because it is heated by the sun • Water is mixed by waves, currents, and tides • Temperature is fairly uniform and averages about 15 degrees Celsius (warmest at equator and coldest at poles) • Only about 2% of the ocean

12. Ocean Water: Temperature and Density • Thermocline/Transition Layer • Temperature decreases quickly with depth • Thermocline • About 18% of the ocean water • Bottom Layer • Sunlight never reaches this layer • Temperatures are very cold (only a few degrees above freezing) • 80% of the ocean water

13. Check In Questions • What is the layer of rapid temperature change with depth called? • What factors affect the density of seawater? How do these two factors affect the density? • Where is most ocean water located? Describe this zone.

14. Ocean Movement

15. Types of Water Movement • There are three general types of ocean water movement: • Waves • Surface currents • Deep-Ocean currents • Each plays a different role in the movement of water in the oceans.

16. Waves • When you go to the beach, what is one of the first things that you notice? • WIND! • It’s always windy by the ocean! Did you know that… • Ocean waves are caused by WIND! • Let’s take a closer look. • A wave is visible evidence of energy passing through water.

17. Surface Currents • Surface currents are movements of water that flow horizontally on the surface of the ocean. • Like with waves, the energy that drives surface ocean currents comes from wind. • Friction is also involved in the development of surface currents. • Remember the video from earlier? The same concept applies.

18. Surface Currents Map What do you notice about the current pattern in the northern hemisphere? What do you notice about the current pattern in the southern hemisphere?

19. Surface Currents • Because of the earth’s rotation, currents are deflected to the RIGHT in the Northern Hemisphere and to the LEFT in the Southern Hemisphere. • This is known as the Coriolis effect. • BOTTOM LINE: The Coriolis effect causes surface ocean currents to be deflected.

20. Surface Currents • Wind can also cause vertical water movements. • Upwelling is the rising of cold water from deeper layers to replace warmer surface water.

21. Surface Currents • Upwelling brings greater concentrations of dissolved nutrients, such as nitrates and phosphates, to the ocean surface.

22. Gyres • Gyres are closed systems of circulating water • The winds blowing from the east are called the Trade Winds. The winds blowing from the west are called Westerly Winds. These opposing wind systems contribute to the formation of  gyres.

23. Deep Ocean Currents In which direction do the warm currents flow? What about the cold currents?

24. Deep-Ocean Currents • Ocean currents that move toward the poles are warm. • An ocean current that is moving toward the equator is cold. • Video showing ocean currents. • Why is the water moving towards the equator cold? Where does it become cold? • It becomes cold when the current moves deeper under the water. Colder water is denser. • What about the warm water? • It warms up when the current brings it up to the surface. This happens around the equator because of exposure to sun.

25. Importance of Ocean Circulation • Transports heat from the equator to the poles, affecting global temperatures • Transports nutrients found predominantly in deep currents to coastal areas, supporting ecosystems • Positive economic effect, allows for continuation of fisheries along coast lines

26. Check In – Use complete sentences • What is the visible evidence of energy passing through water? • Where does the energy come from that drives surface ocean currents? • Which FORCE is involved in the development of surface currents? • What temperature are the currents that move towards the poles? What about the currents that move towards the equator? • What causes surface ocean currents to be deflected?

27. Coastal Climates • Specific heat capacity is amount of heat required to change a substances temperature by 1`C. • Water has a higher specific heat capacity than air. (Water is more resistant to changing temperature.) • The temperatures we experience are due to the amount of heating of the atmosphere above us and the ground and water around us.

28. Coastal Climates • Land heats and cools more rapidly than water • Land also reaches higher and lower temperatures than water • The temperature of the land and water influences the temperature of the air above it • This explains why inland areas experience greater temperature variations than cities near large bodies of water.

29. Sea and Land Breezes • Another process that occurs as a result of differences in density along coastlines are land and sea breezes. • Water has a higher specific heat capacity than sand, meaning it takes more energy to heat 1g of water than it would 1g of sand. • As a result, water also retains heat energy a lot longer as well. • Specific heats: Salt water: 3.93 J/g Sand: .83 J/g • When you might first go to the beach during spring break, say in April when the air starts to warm up, what is the relative temperature of the water?

30. Sea and Land Breezes • During the day, the beach will be warmer than the ocean, causing wind to move from the beach to the ocean, creating a sea breeze. • During the night, the ocean will be warmer than the sand, causing wind to move from the ocean to the beach, causing a land breeze. • The difference in density of these air masses has a very direct effect on the weather experienced along a coastline.

31. Sea and Land Breezes