1. Chapter 5 Water and Seawater
Essentials of Oceanography
7th Edition

2. Atomic structure Atoms are the building blocks of all matter
Nucleus contains:
Neutrons (no charge)
Protons (+ charge)
Outer shell(s) contain:
Electrons (– charge)
Figure 5-1

3. The water molecule Composed of 1 oxygen and 2 hydrogen atoms (H20)
Contains strong (covalent) bonds between atoms
Unusual bend in geometry
Has polarity (oppositely charged ends)
Figure 5-2a

4. Interconnections of water molecules
Polarity causes water molecules to form weak (hydrogen) bonds between water molecules
Water sticks to itself and to other substances
Allows water to be the universal solvent
Figure 5-3

5. Water as a solvent
Water dissolves table salt (NaCl) by attracting oppositely charged particles
Pulls particles out of NaCl structure to dissolve it
Figure 5-4

6. Water in the 3 states of matter
Latent (hidden) heat = energy that is either absorbed or released as water changes state
Figure 5-5

7. The ocean moderates coastal temperatures
Water has high heat capacity, so it can absorb (or release) large quantities of heat without changing temperature
Moderates coastal temperatures
Figure 5-6

8. Hydrogen bonds in H2O
Figure 5-8

9. The formation of ice As water cools to 4°C: Below 4°C:
Molecules slow
Water contracts
Density increases
Below 4°C:
Hydrogen bonds form
Water expands
As water freezes:
Expands by 9%
Figure 5-11

10. Snowflake geometry All snowflakes have 6-sided geometry
Caused by water’s polarity and ability to form hydrogen bonds
Figure 5-12

11. Salinity Salinity = total amount of solid material dissolved in water
Can be determined by measuring water conductivity
Typically expressed in parts per thousand (‰)
Figure 5-15

12. Constituents of ocean salinity
Average seawater salinity = 35‰
Main constituents of ocean salinity:
Chloride (Cl–)
Sodium (Na+)
Sulfate (SO42–)
Magnesium (Mg2+)
Figure 5-13

13. Salinity variations Location/type Salinity Normal open ocean 33-38‰
Baltic Sea
10‰ (brackish)
Red Sea
42‰ (hypersaline)
Great Salt Lake
280‰
Dead Sea
330‰
Tap water
0.8‰ or less
Premium bottled water
0.3‰

14. Ocean buffering Ocean pH = 8.1 (slightly basic)
Buffering protects the ocean from experiencing large pH changes
Figure 5-18

15. Processes affecting seawater salinity
Processes that decrease seawater salinity:
Precipitation
Runoff
Icebergs melting
Sea ice melting
Processes that increase seawater salinity:
Sea ice forming
Evaporation

16. The hydrologic cycle
Figure 5-19

17. Surface salinity variation
Pattern of surface salinity:
Lowest in high latitudes
Highest in the tropics
Dips at the Equator
Surface processes help explain pattern
Figure 5-20

18. Surface salinity variation
High latitudes have low surface salinity
High precipitation and runoff
Low evaporation
Tropics have high surface salinity
High evaporation
Low precipitation
Equator has a dip in surface salinity
High precipitation partially offsets high evaporation

19. Global surface salinity
Figure 5-21

20. Salinity variation with depth
Curves for high and low latitudes begin at different surface salinities
Halocline = layer of rapidly changing salinity
At depth, salinity is uniform
Figure 5-22

21. Seawater density Factors affecting seawater density:
Temperature ↑, Density ↓ (inverse relationship)
Salinity ↑, Density ↑
Pressure ↑, Density ↑
Temperature has the greatest influence on surface seawater density

22. Density and temperature variations with depth
Figure 5-24

23. Pycnocline and thermocline
Pycnocline = layer of rapidly changing density
Thermocline = layer of rapidly changing temperature
Present only in low latitude regions
Barrier to vertical mixing of water and migration of marine life

24. Ocean layering based on density
Mixed surface layer (surface to 300 meters)
Low density; well mixed by waves, currents, tides
Upper water (300 to 1000 meters)
Intermediate density water containing thermocline, pycnocline, and halocline (if present)
Deep water (below 1000 meters)
Cold, high density water involved in deep current movement

25. Seawater desalination
Desalination methods:
Distillation
Solar
Heat
Electrolysis
Reverse osmosis
Freeze separation
Distillation
Figure 5-25
Reverse Osmosis
Figure 5-26

26. Essentials of Oceanography 7th Edition
End of Chapter 5
Essentials of Oceanography
7th Edition