What Creates the Ocean Currents?

Name: _________________________________________________________

What creates the ocean currents?

Ocean water moves on and below the surface in “streams” known as currents. All ocean currents are caused by either wind patterns or by differences in water densities.

Ocean waters move in a continuous cycle. The ocean waters near the equator are heated directly by the sun's rays. Waters at the poles receive less energy from the sun (they are tilted further away from the sun). The deep waters of the oceans come from the surface water cooled in the polar region. Near the poles, the surface water is cooled and becomes heavier. This cool, heavy water sinks and flows towards the equator. Along the way it mixes with warmer, fresh water and gradually rises. Eventually the surface waters are moved by the winds toward the polar regions to complete the cycle. Oceanographers believe that the complete cycle from pole to equator and back again takes hundreds of years. The most saline waters are found at the ocean surface, in regions where the removal of fresh water (by evaporation) is greater than the input of fresh water (by precipitation).

There are two major types of currents that move the waters of the world’s oceans.

• Surface currents are driven by wind and follow global atmospheric patterns. Cold surface currents move from the polar regions to the equatorial zones, and warm surface currents move in the opposite way.

• Deep currents are caused by the differences in water densities. Because all the oceans are connected, all ocean currents interact to form a continuous worldwide pattern of water circulation. The currents flow in certain patterns throughout the world. The currents in the northern hemisphere flow clockwise up from the equator toward the polar regions and then back. While the currents in the southern hemisphere flow in a counter clockwise direction south from the Equator to the polar regions.

Temperature and Density-Driven Currents

Key Concepts:

· ice versus water density

· ocean waters near the equator are heated by the sun's rays

· surface (warm) and bottom (cold) water currents

Objective: To demonstrate and observe the constant exchange of surface and bottom water currents as related to density.

Discussion Questions:

1. Where does the melting ice water go?

2. If the pepper grains represent material on the ocean bottom, what happens to them?

3. What happens to the cold water as it warms up?

Salinity and Density-Driven Currents

Key concepts:

· mixing of waters with different densities

· location of different salinity waters in the worlds ocean

· salinity as a water tracer

Objective: To observe and determine how different salinity waters drive currents.

Discussion Questions:

1. What happens to the high salinity water and why?

2. Where would you expect to find the saltiest waters in the ocean and why?