The ocean's currents are driven by differences in temperature and density. Different masses of water are warmer and less dense than other masses. This water tends to move along the ocean's surface in surface currents. Colder masses and more dense masses of water tend to sink and move along the ocean floor in deep-water currents. Image courtesy of Argonne National Lab

As shown in the diagram above, at several locations warm, less dense water cools, becomes more dense and falls to the ocean floor. At other locations, cold, dense water warms, becomes less dense and rises back to the surface.

This cycling of ocean water along currents is an example of .
A.
absorption
B.
convection
C.
conduction
D.
radiation