1. Marine Hydrology Oceanography Properties of seawater Topics:
Main oceans
Properties of seawater
Composition
Salinity
Sources of sea salt
Density
Factors that impact density
Temperature
Cold water vs. warm water
Layers of temperature
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2. 14.1 The Vast World Ocean Oceanography
 Nearly 71 percent of Earth’s surface is covered by the global ocean.
 Oceanography is a science that draws on the methods and knowledge of geology, chemistry, physics, and biology to study all aspects of world oceans.

3. 14.1 The Vast World Ocean Geography of the Oceans
 The world ocean can be divided into four main ocean basins:
The Pacific Ocean is the largest and deepest
The Atlantic Ocean is about half the size of the Pacific and not quite as deep.
The Indian Ocean, largely a southern hemisphere body, is slightly smaller than the Atlantic.
The Arctic Ocean is the smallest and about 7% of the size of the Pacific.

4. 15.1 The Composition of Seawater
Salinity
15.1 The Composition of Seawater
 Salinity is the total amount of dissolved solid material in water.
Because the proportion of dissolved substances in seawater is so small, oceanographers express salinity as:
parts per thousand (ppt)
Ex: 35g of salt per 1000 grams of water= 35 o/oo

5. Percentage of dissolved salts
 Most of the salt in seawater is sodium chloride, NaCl
Average seawater salinity =
35o/oo
30.6 % Sodium (Na)
55.0 % Chloride (Cl)
14.4% Other
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6. 15.1 The Composition of Seawater
Salinity
15.1 The Composition of Seawater
 Sources of Sea Salt
• 1) Chemical weathering and erosion of rocks on the continents
• 2) Earth’s interior- volcanic activity

7. 15.1 The Composition of Seawater
Salinity
15.1 The Composition of Seawater
 Processes Affecting Salinity
• Processes that decrease salinity:
- Precipitation
- Sea ice melting
- Icebergs melting
- Runoff from land
• Processes that increase salinity:
- Evaporation
- Formation of sea ice

8. Processes that impact salinity
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9. 15.1 The Composition of Seawater
Ocean Temperature Variation
15.1 The Composition of Seawater
 The ocean’s surface water temperature depends on the amount of solar radiation received, which is primarily a function of latitude.

10.  Temperature Variation with Depth
• The thermocline is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of temperature with depth.

11. Variations in Ocean Surface Temperature
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12. Variations in Ocean Water Temperature
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13. 15.1 The Composition of Seawater
Ocean Density Variation
15.1 The Composition of Seawater
 Density is defined as mass per unit volume. It can be thought of as a measure of how heavy something is for its size.
 Factors Affecting Seawater Density
• Seawater density is influenced by two main factors: salinity and temperature.

14. 15.1 The Composition of Seawater
Ocean Density Variation
15.1 The Composition of Seawater
 Density Variation with Depth
• The pycnocline is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of density with depth.

15. Variations in Ocean Water Density
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16. Ocean Layering
 Oceanographers generally recognize a three-layered structure in most parts of the open ocean: a shallow surface mixed zone, a transition zone, and a deep zone.
 Surface Zone
• Shallow (300 to 450 meters)
• Zone of mixing
• Sun-warmed zone

17. 15.1 The Composition of Seawater
Ocean Layering
15.1 The Composition of Seawater
 Transition Zone
• Between surface layer and deep zone
• Thermocline and pycnocline
 Deep Zone
• Sunlight never reaches this zone.
• Temperatures are just a few degrees above freezing.
• Constant high-density water

18. Ocean Zones
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