The Oceans or: Why It’s So Freaking Cold Down There

1. The Oceansor: Why It’s So Freaking Cold Down There Chapter 15

2. Where did the oceans come from? Two sources Comets (frozen water & gas balls) collided with Earth and released their water Meteorites that collided with Earth during its formation contained water

3. Volcanism brought water vapor into the atmosphere Water vapor condensed as the Earth cooled Condensed water rained down to the surface

4. What are the oceans? Recall: the hydrosphere is all of Earth’s water combined (including ice) Oceans make up 97% of all the water on Earth. Oceans cover 71% of Earth’s surface. The oceans are really one connected body of water. The ocean is salty, not pure

5. Major oceans Pacific Atlantic Indian Antarctic

6. Seas Part of same landmass as oceans Smaller than oceans Partially or mostly landlocked Examples: Aral Sea Mediterranean Sea Gulf of Mexico Bering Sea

8. Sea ice Sea ice is constantly changing Grows during winter Shrinks during summer Ice is less dense than water so it floats This helps insulate the oceans and prevent them from freezing entirely

9. sea ice thickness vs. timeanimation

10. What are the properties of sea water? Salinity Salinity is a measure of the mass of dissolved salts per mass of water Measured in parts per thousand (ppt) or percent Recall that percent means parts per hundred Sea water has an average salinity of 35 ppt or 3.5%

11. ocean salinities

12. Salinity varies from place to place Evaporation increases salinity Precipitation & melting sea ice decrease salinity

13. Temperature The sun heats the ocean Water heats up (& cools down) more slowly than air or land So, the ocean acts as an insulator—it resists major changes in temperature This is why coastal areas have smaller swings in temperature between seasons. Different areas of the ocean heat up at different rates This causes convection currents.

14. map of ocean surface temperatures

15. ocean temperature vs. depth

16. Ocean temperatures range from -2C to 30C. Average surface temperature is 15C Temperature decreases with depth The deep ocean is always cold, everywhere on the globe Surface temperatures vary more because of differences in sun exposure

17. Light absorption Water absorbs light Red light gets absorbed first, in shallow waters Blue light gets absorbed last, in deep waters Almost no light penetrates below 100 meters

18. light absorption at various depths

19. What are water masses? The ocean is separated into layers because of different densities Temperature & salinity affect density Colder, saltier water is denser and sinks Warmer, less salty water is less dense and floats A thermocline is an area where water rapidly decreases in temperature with depth A halocline is an area where water rapidly changes salinity with depth

20. ocean layering - temperature

21. Cold water comes from the polar seas and migrates along the sea floor toward the equator Antarctic Bottom Water: from freezing Antarctic seas North Atlantic Deep Water: from Greenland Antarctic Intermediate Water: from winter water in the Antarctic Water Colder water pushes warmer water toward the surface

22. major water masses

23. Currents affect the locations of different layers Living organisms are adapted to specific ocean layers Plants are found only in the sunlit zone Most organisms live close to the surface

24. organisms & ocean zones

25. creatures of the deep seavideo clip

26. How does the ocean move? Waves A wave is a rhythmic movement that carries energy through ocean water. Waves are causes by wind or earthquakes. The water moves up & down in circle, but the energy moves forward. Waves break when they experience friction against the ocean floor in shallower water.

27. waves moving & breakinganimation • Animation will open in an external window (exit slideshow to view)

28. Currents A current is the movement of a body of water in a definite direction Density currents are caused by differences in density Ex. Antarctic Bottom Water sinking Surface currents are driven by wind Ex. Trade winds in the tropics blow from east to west and push tropical waters from east to west

29. major ocean currentsanimation

30. Surface currents cause upwelling—the movement of lower waters toward the surface

31. Gyres A gyre is a circular current Gyres are the result of currents being deflected by continents There are five major gyres

32. Coriolis effect The Coriolis effect is the deflection of water (and air) to the right above the equator and to the left below the equator It is caused by Earth’s rotation The Coriolis effect causes: Clockwise gyres in the northern hemisphere Counterclockwise gyres in the southern hemisphere Remember that continents deflect this movement!

33. The Coriolis Effectanimation

34. Tides Tides are the periodic rise and fall of sea level. The difference between high and low tide (tidal range) varies from place to place. Tides are caused by the gravitational attraction among the Earth, moon, and sun. The moon & sun pull on Earth’s oceans. High tide occurs where the oceans bulge.

35. effect of sun & moon on tidesanimation