1. Chapter 15 Earth’s Oceans

2. The Global Ocean One vast body of water covering more than two thirds of Earth’s surface Oceans contain 97% of the water on Earth Oceanographers study the oceans: – Water chemistry – Wave action – Marine organisms – Sediments

3. Data Collection Surface – Sonar—find the depth of the ocean, map undersea mountain ranges – Floats and Satellites (TOPEX/Poseidon)—map temperature, salinity, wave motion Deep water—unmanned and manned submersibles (Alvin) Computers—model information about tides, tsunamis, pollution, climate change

4. Research Ships Sentry and AlvinHMS Challenger

5. Origin of the Oceans Oceans have existed almost since the beginning of Earth’s geologic history. Evidence indicates that the source of the water on Earth was – volcanic eruptions (water vapor) – impacts with comets and meteorites

6. Distribution of Earth’s Water The southern hemisphere has much more water than the northern hemisphere.

7. Sea level changes (due to melting glaciers and thermal expansion)

8. Major Oceans Pacific Atlantic Indian Arctic Southern

9. Chemical Composition of Seawater Water NaCl MgCl 2 KCl CaCl 2 Average salt concentration is 3.5% (varies from 3.2% to 3.7%) Salt added and removed is in equilibrium

10. Ocean Stratification (Layering) Ocean water forms layers based on density, caused by temperature and salinity differences

11. Water Masses AABW: Antarctic Bottom Water—coldest and most dense NADW: North Atlantic Deep Water—less dense than AABW

12. Ocean Movements: Waves

13. Waves Shallow water causes waves to slow down

14. Ocean Movements: Tides Tides are caused by gravitational effect of both the Moon and the Sun Spring Tides: higher tidal range Neap tides: lower tidal ranges

15. Ocean Movements: Currents Gyres (horizontal surface currents) transfer heat from equator to poles

16. Ocean Movements: Currents Density currents (ocean conveyor belt) move vertically as well as horizontally