School Email Exchange

Could you explain how the Pacific’s ocean currents bring all this debris together?

Posted on November 10 2012

Question submitted by Trinity-Pawling School

The North Pacific subtropical gyre consists of a clockwise circulation around the boundaries of the North Pacific basin that is ultimately driven by the surface winds blowing on the water.  In the center of the gyre the surface ocean currents converge, or flow towards one another, because of the wind patterns and the friction between the wind and the surface water of the ocean.  This region is called the subtropical convergence zone, and is typically found close to 30º latitude in all subtropical oceans.  The track of this expedition was designed to sample along this convergence zone, where we expect to find the highest accumulation of floating plastic debris.

However, it is important to note that not all debris is in one localized place in the center of the gyre.  We have found large variability (regions with relatively high concentrations of plastic very close to regions with much lower plastic concentrations).  The term oceanographers use to describe this variability is patchiness.  This is a different sense of the word "patch" than in the term, 'Great Pacific Garbage Patch'.

For a slightly more detailed discussion about the subtropical gyre circulation, please visit a previous post from our 2010 North Atlantic Expedition.