Ocean Currents – Narrated PowerPoint
Name: ________________________
Fill in the blanks below as you watch the narrated powerpoint about ocean currents.
1. The power of currents to ____________________ and control the seas is unmatched.
2. Currents are cohesive streams of sea water that _____________________ through the oceans.
Some are short lived and small, while others are vast flows that take centuries to complete a circuit
of the globe.
3. Currents are caused by:
1. __________________________
2. __________________________
3. __________________________
4. There are two distinct current systems in the oceans:
1. Surface Currents (_______________ circulation) – Stirs a relatively thin upper layer of the sea
2. Deep Ocean Currents (_____________ circulation) – sweeps along the deep sea floor
Part II: Surface Currents
5. The dominant pattern of surface circulation is the ___________________; a well-organized,
roughly circular flow. Five enormous gyres spin in subtropical waters. Two in the Atlantic and the
Pacific oceans, and one in the Indian ocean.
6. _______________ is the most important cause of surface currents. When strong, sustained wind
blows across the surface of the sea, friction drags a thin layer of water into motion. The movement
of the very top layer of the sea pulls on the layer just beneath, which then in turn starts the layer
under it moving.
7. Surface currents are also triggered by _____________________.
8. The currents move at an angle to the force that generates them; a phenomenon called the
Coriolis effect. Coriolis effect diverts currents and causes them to move in a circular motion.
9. The movements of currents are also constrained by the _________________ of the ocean basins
(seafloor topography). When a current runs into a continent, it must turn aside.
10. The complex interplay between wind, gravity, Coriolis effect, and topography, determines the
location, size, shape, and direction of the surface current gyres.
Part II: Deep Currents
11. ___________________ currents flow along coastlines when waves run into the shore at an
angle. They pull those great volumes of sand along the shore, causing beaches to disappear, and
harbours to fill in.
12. ______________ currents form where obstacles channel water away from the shoreline.
13. Upwelling currents occur when winds push surface water away from the shore, and deeper
water rises to fill the gap. These currents bring __________________ to the surface.
14. Deep currents twist together into a continuous stream that loops through all the oceans, called
the ___________________________________________. The conveyor belt slowly but steadily
empties one ocean into another. This vast global circulation is driven by density variations in the
ocean. This depends on ________________________ and salinity (saltiness).
15. As sea water gets colder and saltier, its density ________________________, and it starts to
sink towards the bottom. Surface water is pulled in to replace the sinking water, and eventually it
becomes cold and salty enough to sink – thus a current begins.
SUMMARY OF OCEAN CURRENTS

There are two types of ocean currents:
o Surface currents
o Deep Currents

The three main causes of surface currents are:
o Wind
o Gravity
o Density Differences (due to temperature and salinity differences)
o Seafloor Topography (the shape of the ocean basin)

The Coriolis Effect deflects moving objects when they are viewed from a rotating reference
frame. For example, an airplane doesn’t move exactly from point A to point B in a straight
line because the world is spinning while it is flying, so the airplane has to adjust its path.