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!
