Properties of Ocean Water

1. Properties of Ocean Water Chapter 21.1

2. Ocean Water • Ocean water has both chemical and physical properties. • Chemical properties are those characteristics that determine the ocean water’s composition and that enable it to dissolve other substances. • Physical properties are those characteristics, such as temperature, density, and color than can be used to describe ocean water.

3. Ocean Water • Composition of Ocean Water • The earth’s rivers carry about 400 billion kilograms of dissolved solids into the ocean, and most of these dissolved solids are salts. • When water evaporates out of the ocean, the dissolved solids are left behind.

4. Ocean Water • Gases also enter the ocean water through rivers, stream, geothermal activity, or straight from the atmosphere. • Gas is constantly released into the ocean through geothermal vents near mid-ocean ridges and seamounts.

5. Ocean Water • While billions of kilograms of substances are added to the ocean water each year, the ocean water has remained unchanged for millions of years. • The ocean has reached an equilibrium with its environment. Much of the materials entering the ocean are used by the life in the ocean.

6. Salinity • Salinity of Ocean Water • Dissolved solids make up about 3.5% of the mass of the ocean water. • When sodium chloride, table salt, is dissolved in water it breaks down, and about 78% of the ocean’s dissolved solids are made up of the individual sodium and chlorine ions.

7. Salinity • Salinity is the amount of dissolved solids present in ocean water since most of the solids are in the form of salts. • Salinity is defined as the number of grams of dissolved solids in 1kg of ocean water.

8. Salinity C. Evaporation and freezing increase the salinity of ocean water since only the water molecules are removed during these processes. • Salinity values vary between depth and temperatures. • Tropical waters have a higher salinity at the surface than do polar waters, and surface waters have a higher salinity than deep water since water is constantly evaporating at the surface.

9. Salinity • Salinity values also vary greatly over the global ocean. • For example, the salinity of the Red Sea is over 40%, due to the hot and dry climate, and the Baltic Sea is about 20% due to melting and runoff of nearby rivers and streams.

10. Temperature • Temperature of Ocean Water • Ocean water has the ability to absorb the infrared wavelengths of the sun which heat the water. • Infrared rays are completely absorbed within the upper zone of ocean water, however, this dramatically decreases as depth increases.

11. Temperature • The movement of water in the ocean thoroughly mixes the warmed surface water which distributes the heat to a depth of 100m to 300m. • Depending on latitude, the temperature of this zone of the ocean stays fairly consistent.

12. Thermocline • A thermocline is the zone of rapid temperature change, decrease, and occurs at a depth of 300m to 500m. • The thermocline exists because the water near the surface becomes less dense as it is warmed by heat from the sun and cannot mix easily with the cold, dense water below. • Below the thermocline the water temperature continues to drop slightly until it reaches just above freezing for those water conditions. • Thermoclines are also present in most lakes.

13. Density • Density of Ocean Water • Density is the mass of a substance per unit volume. • For example, 1 cubic centimeter of pure water has a mass of 1kg, and its density is 1.00g/cm3. • Two factors affect the density of ocean water: salinity and temperature. • Dissolved solids add mass to the water in direct proportion to the amount of each one present. These dissolved solids make ocean water more dense than fresh water. • Ocean water has a density of about 1.026 g/cm3 and 1.028 g/cm3.

14. Density • Ocean water becomes more dense as it becomes colder and less dense as it becomes warmer. • Temperature affects the density of ocean water more than salinity. • Therefore, the densest oceans are found near the polar regions.

15. Color • Color of Ocean Water • The ocean appears to have a blue color because every color other than blue is absorbed, and only blue wavelengths tend to be reflected. • When you look straight down the water tends to be a dark blue because blue is the last color to be absorbed. • When you look at an angle, the ocean water tends to sparkle due to the blue wavelengths being reflected off the surface.