View full lesson: http://ed.ted.com/lessons/the-motion-of-the-ocean-the-concentration-gradient-sasha-wright

The constant motion of our oceans represents a vast and complicated system involving many different drivers. Sasha Wright explains the physics behind one of those drivers -- the concentration gradient -- and illustrates how our oceans are continually engaging in a universal struggle for space.

Lesson by Sasha Wright, animation by Andrew Foerster.