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

https://water.usgs.gov/edu/watercyclehi.html

• 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