Chapter 5: Chemical Oceanography

Learning Objectives

After reading this chapter you should:

  • understand some of the unique properties of water
  • understand hydrogen bonds and how they affect water’s properties
  • understand the concept of outgassing
  • understand the concept of residence time
  • understand how salinity is measured and calculated
  • know the major ions in seawater
  • understand the rule of constant proportions
  • understand how and why salinity changes as a function of latitude and depth
  • know the processes responsible for dissolved gases in the ocean
  • be able to produce and describe depth profiles for oxygen, carbon dioxide, and nutrients
  • understand the role of carbon dioxide as a buffer in the ocean
  • understand the issue of ocean acidification

Ask anyone to describe the oceans, and it is very likely that among the first words you hear will be “water” and “salty”. Despite being perhaps our most vital natural resource, water often does not get the credit it deserves. We describe food or drinks we don’t like as “watery”, and we deride a perceived lack of strength as “weak as water” or “watered down”. But in reality, water is an amazing substance, characterized by a number of unique properties that make life possible (it has been remarked that life is just water’s way of moving itself around). And it is the salty nature of the ocean that sets it apart from most other bodies of water on Earth, as anyone who accidentally swallowed a mouthful of seawater at the beach will tell you. But ocean water contains a vast array of substances besides salt, and the field of chemical oceanography examines how these various ions, elements, gases, and other substances interact with each other, with marine organisms and oceanographic processes, and with the seawater itself.

This chapter begins with an introduction to the properties of water, before examining the origin and distribution of salts in the oceans. It then discusses the fates of dissolved gases in the ocean, particularly those that are important for marine life. The chapter concludes with a look at the current environmental issues associated with ocean acidification.

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Introduction to Oceanography by Paul Webb is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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