Global Ocean Currents. Photo Credit: waydownsouth.wikispaces.com

It’s a popular opinion that we have only scratched the surface of knowing everything our oceans have to offer.  What we do know is how the ocean moves and why.  Ocean currents are divided into 2 main categories: surface and deep.

Deep currents are ocean currents that are usually more than 100 meters deep.  Deep water currents travel the globe with a force 16 times as strong as all the world’s rivers combined.  Deep water current is driven by density differences in the water.  These movements based on density are also known as Thermohaline Circulation because water density depends on its temperature (thermo) and salinity (haline).  The density of this deep water is much greater than that on the surface so the speed of this current is slow however the amount of water being moved is more than 100 times the flow of the amazon river!

You’re likely familiar with coastal currents if you have ever gone to the beach.  These are in the category of surface currents.  Surface currents are ocean currents that occur at 328 feet (100 meters) deep or above.  Unlike deep water currents, where differences in density causes movement, surface current movement is due to wind that flows across the top of the water’s surface.

Coriolis effect on atmospheric circulation. Photo Credit: oceanservice.noaa.gov

The picture above depicts the Coriolis Effect.  Winds from the equator direct towards to the north and south poles.  If there was no rotation of the earth the winds would shoot towards the equator in a straight line.  However, because the Earth rotates on its axis, circulating air is deflected toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere.  This deflection is called the Coriolis effect.  This air drags on the oceans surface dragging it in its direction giving the current directions you see today.