Why does water in ocean currents flow the way it does?

Question

Why does water in ocean currents flow the way it does? I know gravity, density and the other factors, but could someone tell me in common everyday language as well as scientifically?

Answer 1

The simple answer is that the wind drives the currents. The currents will blow in a direction close to wind's.

The more detailed explanation involves wind piling up water in a certain region and temperature conditions interacting together to produce a sea surface slope (a bulge of water). When water flows down the slope, it's deflected by the Coriolis effect. This net effect causes water to flow around that bulge of water, forming your gyres and geostrophic currents.