Chapter 3: Chemical and Physical Features of Seawater and The World Ocean
  • The Waters of the Ocean
  • The Unique Nature of Pure Water
  • The Three States of Water

    Heat and Water

    Water as a Solvent

  • Seawater

  • Salt Composition

    Salinity, Temperature, and Density

    Dissolved Gases



  • Motion in the Ocean

  • Surface Circulation

    The Coreolis Effect

    Wind Patterns

    Surface Currents



  • Why Are There Tides?

    Tides in the Real World

  • Vertical Motion and the Three-Layered Ocean

  • Stability and Overturn

    The Three-layered Ocean


    Boxed Readings:


    Chapter Summary

    Chapter 3 outlines the basic chemical and physical characteristics of the ocean, stressing their relevance to the distribution of life in the marine environment.


    Answers to Critical Thinking Questions

    1. The winter of 1984-85 was particularly cold in Europe. The northern part of the Black Sea, which lies between the Ukraine, Russia, and Turkey, froze, which is rare in the normally mild climate. The Adriatic Sea, located to the east, had just as cold a winter but never froze. The Black Sea has an unusually low salinity of about 18o/oo. What would you guess about the salinity of the Adriatic?


    The salinity of the Adriatic Sea has to be higher. It actually varies between 38-39o/oo in the south, to 33-25o/oo in the north.


    2. Just for the fun of it, someone walking along the shore in Beaufort, South Carolina, throws a bottle with a message in it into the sea. Some time later, someone in Perth, on the west coast of Australia, finds the bottle. Referring to Appendix B of this book or Figure 3.19, can you trace the path the bottle probably took?


    The most probably route is: Gulf Stream, Canary Current to the Equator, South Equatorial Current, Brazil Current along the east coast of South America, Antarctic Circumpolar Current, and finally north along the west coast of Australia.


    3. If you owned a seaside home and a bad storm brought heavy winds and high surf to your coastline, would you prefer it to be during new moon or a quarter moon? Why?


    A storm during a quarter moon would be less destructive because tidal range is at its lowest. The highest tides are observed during new and full moons. A storm during these periods would be more destructive since storms cause tides that are higher than predicted tides.


    4. Most tsunamis occur in the Pacific Ocean, as indicated by the map in the Waves that Kill box reading. How would you explain this?


    The Pacific basin is almost entirely circled by boundaries of plates and hence areas of frequent earthquakes (see Figs. 2.7 and 2.10).