1. Ch. 21.1 Properties of Ocean Water
Ch. 21 Ocean Water
Ch Properties of Ocean Water

2. Ocean water has both chemical and physical properties.
Chemical properties include composition, salinity, and the ability to dissolve other substances.
Physical properties include temperature, density, and color.

3. Composition of Ocean Water
Ocean water contains dissolved salts, minerals, and gases.
400 billion kilograms of salts carried to oceans by rivers each year.
Salts and minerals remain in ocean when water evaporates.
Amount of dissolved substances has remained constant for millions of years.

4. Processes that add salts and minerals are balanced by processes that remove dissolved material (formation of sediments; use by marine plants and animals).

5. Elements in Ocean Water
Ocean water is 96.5 % H20.
About 75 chemical elements, mostly in dissolved ionic form.
The 6 most abundant dissolved elements are chlorine, sodium, magnesium, sulfur, calcium, and potassium.
Trace elements include gold, zinc, and phosphorus.

6. Dissolved Gases
Gases found in the atmosphere are also found dissolved in the ocean (Nitrogen, Oxygen, Carbon Dioxide (CO2)).
Carbon Dioxide dissolves the most easily in ocean water.
Most dissolved oxygen is at the surface, where the ocean is in contact with the air.
Unlike solids, gases dissolve better in cold water.

7. Gases can move back and forth between the ocean and the atmosphere.

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9. Salinity of Ocean Water
Salinity is the amount of dissolved solids in ocean water, so named because most of the solids are in the form of salts.
Defined as number of grams of dissolved solids per kilogram of ocean water.
If 1 kg of ocean water was evaporated, and 35 grams of solids remained, salinity would be 35 (salinity = 35 0/00).

10. Both evaporation and freezing increase salinity.
In the tropics, where evaporation is high, salinity at the surface is also high.
Generally, surface water has higher salinity than deeper water.
Average ocean salinity is 34.7, with average range from 33 to 36.

11. There may be extremes due to either very high evaporation, or large additions of fresh water.

12. Temperature of Ocean Water
Solar heating raises the surface temperature of the ocean.
Ocean water movement mixes the warm water to a depth of m.
Overall warmer surface temp. near the equator than the poles…it even freezes at the poles, forming pack ice.

13. The Thermocline
The depth below the warm mixing zone, where the temperature drops rapidly with depth, is called the thermocline.

14. Density of Ocean Water Density is mass per unit volume.
Pure water has density of 1g/cm3.
Due to dissolved solids, ocean water has a density between and g/cm3.
Temperature also affects density, with dense cold water usually sinking to the ocean floors in the polar regions.

15. Color of Ocean Water
Most wavelengths of light are absorbed by ocean water, except blue, which is reflected, so the ocean appears blue.
Suspended particles or marine organisms may cause the ocean to appear green or brown.