Surface current are wind generated circular rotations of water. These patterns, called gyres, develop their shape as a result of wind stresses. The Ekman Spiral causes a current to flow at an angle to the area’s prevailing winds. Surface currents are responsive to changes in seasons and move somewhat, which is most apparent in the Equatorial currents. Involving approximately 10% of all ocean water, currents are restricted to the top 400 meters of the water column. Transporting heat from the Equator towards the polar regions and moving colder water from the poles towards the Equator, wind-driven open-ocean surface currents move at speeds approximately 1/100th of the wind speed at 10 meters above the surface. Major ocean currents transport large volumes of water. For example, the Antarctic Circumpolar Current transports water at approximately 4 km per hour.
Many organizations follow the surface movement of the oceans. NOAA’s OSCAR program tracks the surface currents with satellite altimeters. NOAA and Atlantic Oceanographic and Meteorological Laboratory launch drifter buoys that are transported around the oceans. Classrooms can adopt and track a drifter buoy. Many people collect items that wash up onto the beach which have traveled through currents, called flotsam. Global armature networks look for flotsam and send out world wide alerts when new materials appear. Scientists interested in the movement of Arctic ice track how the Arctic Current moves have placed buoys and ships in the ice to observe how the current moves the ice over time.
Image from Windows to the Universe (http://www.windows.ucar.edu/tour/link=/earth/Water/images/surface_currents_lg_jpg_image.html)
With the world map, discuss how the atmosphere heats unequally. Discuss how the Coriolis Effect moves water.
Demonstrate: Ask a student to place the small paper pieces into the glass container and place it on the overhead. Use the straw to blow on one side of the container. Observe the movement of the pieces as a result. Ask students for observations. This is what happens in the ocean but on a much larger scale.
Provide each student with a copy of the world map. Ask students to identify the Equator. Make a legend on the side of the map- cold water will be represented by blue, warm by red.
Read current descriptions to students. As a group, decide where to place the current and how to represent the size and direction of the flow. Name the current.
What patterns do the currents make? Gyres. How does water at the poles moving toward the Equator different in each hemisphere? Northern Hemisphere it moves to the right, Southern Hemisphere it moves to the left.
What would happen if you dropped a whole truck of toy ducks into the water near the coast of Peru? Where would they eventually go? What currents would they travel through?
Predict what occurs in the northern Indian Ocean without the influence of cold polar water.
How does the geography of the land affect the direction of the wind and water? Why is the flow different between currents? Find and identify the largest current. Explain why this occurs. Currents flow fastest when a large volume of water is forced to flow through a narrow gap.
Can be done with a large world map as a group.
Look up the Arctic currents and place them on the map. Who might depend on the seasonal ice movement?
Add smaller currents and research the names/origin
Research the rate of transport for each current
Look up the Great Sneaker spills. Join Beachcombers Alert (www.beachcombers.org).