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The Oceans
Chapter 15
What comes to mind when you think “Oceans”?
Where did the oceans come from?
• Water has been present since Earth formed but not in liquid form.
• Volcanoes released water vapor into the atmosphere
• Water vapor condensed as the Earth cooled
• Condensed water rained down to the surface
What are the oceans?
• Hydrosphere is all of Earth’s water combined (including ice)
• Oceans make up 97% of all the water on Earth.
• Oceans cover 71% of Earth’s surface.
• The oceans are really one connected body of water.
• The ocean is salty, not pure
• Major oceans
• Pacific
• Atlantic
• Indian
• Antarctic
• Seas
• Smaller than oceans
• Partially or totally landlocked
• Examples:
• Mediterranean Sea
• Gulf of Mexico
• Bering Sea
• Caribbean Sea
• Sea ice
• Sea ice is constantly changing
• Grows during winter
• Shrinks during summer
• Overall, ice is decreasing globally.
• Ice is less dense than water so it floats
• This helps insulate the oceans and prevent them from freezing entirely
sea ice thickness vs. time animation
What are the properties of sea water?
• Salinity
• Salinity is a measure of the mass of dissolved salts per mass of water
• Measured in parts per thousand (ppt) or percent
• Recall that percent means parts per hundred
• Sea water has an average salinity of 35 ppt or 3.5%
ocean salinities
• Salinity varies from place to place
• Evaporation increases salinity
• Precipitation & melting sea ice decrease salinity
• Temperature
• The sun heats the ocean
• Water heats up more slowly than air or land
• So, the ocean acts as an insulator—it resists major changes in temperature
• This is why coastal areas have smaller swings in temperature between seasons.
• At the equator, the ocean gets more direct sunlight so it’s warmer
map of ocean surface temperatures
ocean temperature vs. depth
• Ocean temperatures range from -2C to 30C. Average temp is 15C
• Temperature decreases with depth
• The deep ocean is always cold, everywhere on the globe
• Surface temperatures vary more because of differences in sun exposure
• Light absorption
• Water absorbs light
• Red light gets absorbed first, in shallow waters
• Blue light gets absorbed last, in deep waters
• Almost no light penetrates below 100 meters
light absorption at various depths
What creates ocean zones?
• Ocean zones are determined by light and distance from the coast. • Most organisms live at the surface
where it’s light and warm.
organisms & ocean zones
creatures of the deep sea video clip
How does the ocean move?
• Waves
• All waves transfer energy
• Waves are causes by wind or earthquakes (tsunami!).
• The water moves up & down in circle, but the energy moves forward.
• Waves break when they experience friction against the ocean floor in shallower water.
waves moving & breaking animation
• Animation will open in an external window (exit slideshow to view)
• Currents
• A current is the movement of a body of water in a specific direction
• Density currents
• Ex. Cold salty Arctic water sinks
• Surface currents are driven by wind
• Ex. Trade winds in the tropics
major ocean currents animation
• Gyres
• A gyre is a circular current
• Gyres are the result of currents being deflected by continents
• There are five major gyres
Now, use your book to label the following on your “Global Winds and
Ocean Currents” worksheet:
• The California Current
• The North Atlantic Current
• The North Pacific Gyre
• The South Pacific Gyre
• The North Atlantic Gyre
• The South Atlantic Gyre
• The Indian Ocean Gyre
• Tides
• Tides are the periodic rise and fall of sea level.
• Tides are caused by the gravitational attraction among the Earth, moon, and sun.
• The moon & sun pull on Earth’s oceans.
• High tide occurs where the oceans bulge.
effect of sun & moon on tides animation