Oceans cover most (~70%) of Earth’s surface, thus, Earth is sometimes called the ‘water planet’.  Oceans affect all our lives by providing food, allowing transport of goods, and affecting weather and climate.

Oceanography: the scientific study of the ocean and seas

Properties of Water

*Water is an extremely unique compound!

-Solid water (ice) is actually less dense than liquid water.  Thus, ice floats on water!

WHY? When water freezes, the molecules actually spread out in a rigid framework, creating more void space!

-Water molecules are also held together by strong hydrogen bonds!  This makes water very stable and less likely to change forms over a wide range of temperatures!

-Thus, water remains a liquid from 0°C to 100°C!

Properties of Ocean Water

I. Salinity

-a measure of the dissolved salts in water

-expressed in parts per thousand (/00)

*35g/1000g seawater = 35/00

-important in identifying water masses

water mass: a body of water with distinct properties based on where it originates

-raises the boiling point and lowers the freezing point of seawater!

-Seawater remains a liquid from -2°C to 100.3°C

-85% of ocean’s salt is NaCl; table salt!

-Seawater contains over 70 other elements

A. Variations in Salinity

*Water masses in different parts of the world have different salinities based on local conditions.

-Extremely HOT/ DRY climates

  • Above average salinity
  • Oceans lose water rapidly through evaporation, leaving salts behind
  • Ex- Mediterranean and Red Seas

-Extremely COLD climates

  • Above average salinity
  • Seawater freezes, leaving salts behind
  • Ex- Polar waters

-Areas w/large amounts of freshwater

  • Below average salinity
  • Rivers and glaciers drain into ocean
  • Lots of rainfall in/near ocean
  • Ex- Baltic Sea and near Equator

-Salt composition has not changed much in the past 200 million years

  • Enter = volcanic vents; erosion of land (minerals runoff); organisms decay
  • Exit = plants and animals uptake; settle onto the ocean bottom

II. Temperature

-Almost all of the energy that heats the oceans comes from the sun.

-Most sunlight is absorbed in the 1st few meters of ocean water.

-Ocean temperature decreases rapidly with depth.

-Ocean is divided into 3 layers:

A. The Surface

-Warmed by sunlight

-Also called the mixed layer because wind and waves mix the heat evenly

-Only about 2% of the ocean’s volume

-From 0 to 300 meters deep

-Very important to life!

Phytoplankton live here, and make up the base of the ocean’s food chain!

B. The Middle Zone

-Receives only some sunlight

-Also called the thermocline because temperature changes rapidly here

-From 300 to 1000 meters deep

-Bottom of this layer is very cold (5°C)

C. Deep Water

-Receives little to no sunlight

-Water is very cold (2°C) and fairly constant all over the globe

-A few species do manage to live here!

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