Basics of the Ocean and Water Properties

Earth's Surface Composition

• Ocean Coverage: Oceans cover 70.8% of Earth's surface.
• Land Coverage: Land covers 29.2% of Earth's surface.
• Subdivision of Oceans:
  • Four main oceans: Pacific, Atlantic, Indian, and Arctic.
  • Additional Ocean: Southern Ocean surrounding Antarctica.
• Ocean Depth: Average depth is 12,000 feet, deeper than average land height (3000 feet).
• Deepest Point: Marianas Trench at 36,000+ feet, deeper than Mount Everest is high.

Water Molecule and Properties

• Basic Definitions:
  • Atom: Smallest unit retaining chemical properties.
  • Molecule: Group of atoms bonded chemically.
• Water Molecule (H₂O):
  • Composed of 2 hydrogen atoms and 1 oxygen atom.
  • Structure resembles "Mickey Mouse" ears (dipole molecule).
  • Connected by covalent bonds where electrons are shared.
• Properties of Water:
  • Hydrogen Bonds: Attraction between hydrogen (positive) and oxygen (negative) atoms in adjacent molecules.
  • High Heat Capacity: Amount of energy to raise 1g of water by 1°C.
  • Comparison: Water's heat capacity is higher than most substances (e.g., aluminum, granite).

Effects on Climate

• Temperature Range:
  • Coastal cities have lower temperature ranges due to ocean's moderating effect.
  • Interior cities display larger temperature variations.

Density of Water

• Maximum Density: At 4°C (39°F), water is densest.
• Ice Density: Less than liquid water, causing ice to float.
• Implication: Allows water at 4°C to sink to ocean's bottom.

Salinity

• Definition: Mass of dissolved solids in grams per kilogram of seawater.
• Measurement Units: Parts per thousand (ppt), g/kg, or a modified percent symbol.
• Average Ocean Salinity: 35 ppt.
• Factors Affecting Salinity:
  • Increase: Adding salt (e.g., volcanic eruptions) or removing fresh water (evaporation, sea ice formation).
  • Decrease: Adding fresh water (rain, runoff) or removing salt (salt spray, chemical reactions).
• Salinity Patterns:
  • High at 30° N/S due to evaporation.
  • Low at equator and 60° N/S due to precipitation.

Global Ocean Properties

• Temperature and Salinity:
  • Sea Surface Temperature: Warmer near equator, colder near poles.
  • Salinity Distribution: High in dry regions, low in rainy regions.
• Density:
  • Factors: Affected by temperature and salinity.
  • Colder and Saltier Water: More dense.
  • Layering: Denser water sinks beneath less dense water.
  • Pycocline Layer: Boundary where density rapidly changes, separating surface from deep water.
  • Deep Ocean: Mostly cold, dense water formed in polar regions.

Test Yourself

1. Draw a labeled diagram of a water molecule.
2. Calculate the salinity of a body of water with 10g of salt in 5kg of water.
3. Does salinity increase or decrease as sea ice melts? Why?
4. Why is sea surface temperature related to latitude?
5. Identify regions with highest and lowest salinity and explain why.