Dive Into Your Imagination

August 7, 2009

For the past six days I have been surrounded by miles and miles of endless blue ocean. We have been traveling 10 knots a day and approaching the targeted area of our expedition. I feel a freedom out in the ocean that does not exist when I am on land.  I stare out at the surface of the ocean we are merely skimming and in my mind I can visualize the volcanic mountains, schools of fish and creatures living below, and yet we see nothing from above except the sea meeting the sky.  We are traveling the last 200 miles toward the area these scientists believe has the highest accumulation of plastic.  To fully understand where we are heading and why we may find plastic here, it is important to understand the physical qualities of this part of the ocean.

What is a gyre?
A gyre is made of oceanic currents.  There are 5 major oceanic gyres in the world.  It is a rotating water mass, like a slow spinning vortex, created due to surface winds pushing on water, pressure gradient forces, and The Coriolis Effect.

The Coriolis Effect is caused by the spin of our planet on its axis.  Imagine an object, such as a ship or a mass of water moving straight across the planet.  Due to The Coriolis Effect, the object gets deflected.  Objects are deflected by a net flow of ninety degrees to the right of surface winds in the Northern hemisphere and the left in the Southern hemisphere.  This only affects the top 400 meters of water.

In a Pressure Gradient Force, objects move from a position of high pressure to a position of low pressure. 

What creates the North Pacific Gyre?
The westerlies to the north of the gyre blow Eastward, and the easterly trade winds to the south of the gyre blow Westward. These winds blow water on the surface of the ocean.  The Coriolis Effect causes the water to be deflected a net 90 degrees to the right of the surface winds.  This creates a high pressure zone in the center, meaning water piles up in the middle of the Pacific Ocean, creating a hill of water.

Because of pressure gradient forces, water will want to naturally flow down this hill.  When the water flows down the hill of water from the pressure gradient force, the Coriolis effect wants to do the opposite and push the water back up the hill.  When these two forces balance, it creates a flow that moves across the hill instead of up or down.

The continuous curve of the gyre is always influenced by the deflection of The Coriolis Effect, and is greatly influenced by land masses, which are natural barriers to the flow of water.  Once the water hits a continent, it can no longer continue on its current path and gets deflected.  This means that once the water flowing West across the equator reaches Asia, it is deflected Northward.  This same pattern continues throughout the rest of the gyre and because of this movement of water, there are four distinct currents: The North Pacific, California, North Equatorial, and Kuroshio currents.

The North Pacific Gyre is not the only Gyre in the world.  There are actually 5 total in our world Ocean: The North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian Ocean.

Why is the North Pacific Gyre a focus of study?
The North Pacific Gyre is the location of what is now known as The Garbage Patch.  Dr. Charles Moore from Algalita Marine Research Foundation has been sailing out to the North Pacific Gyre for the past 10 years after he discovered that the Pacific Ocean was filled with tiny pieces of plastic he termed confetti.

With the need for more scientific data, the SEAPLEX expedition was formed by a group of graduate students from Scripps Institution of Oceanography.  Each scientist aboard had a different focus and reason why plastic is important to their research.  Study focuses ranged from seabirds and marine mammals research to bacteria, phytoplankton, zooplankton, marine debris and fouling communities, to discovering the effects of pollutants at the top of the food chain.  This affects us from the air we breathe to the food we eat.

Project Kaisei helped fund two expeditions to the North Pacific Gyre during August 2009: the SEAPLEX expedition aboard the New Horizon and the Kaisei.  Project Kaisei was founded to create solutions to the marine debris in our ocean and to clean up the garbage patch.

Why does plastic accumulate in the North Pacific Gyre?
The hill of water is created by a high pressure weather system.  When The Coriolis Effect pushes new water to the center, the old water is pushed down and sinks but leaves the trash behind.  The new water carries new plastic with it and deposits it in the center before it too sinks.  This means there is a constant source of plastic and trash supplied to the convergence zone, but it is never carried away.  While many people believe the gyre to have a role in collecting trash, it is actually the convergence zone that causes the accumulation.  Trash can be found throughout the gyre, but the highest concentration is believed to be in the Subtropical Convergence Zone

The Subtropical Convergence Zone is a high pressure weather zone that is created by winds converging in one area, and in turn leads to buildup of surface water.  The Subtropical Convergence Zone is found in the North Pacific Gyre, and can be contrasted to the Intertropical Convergence Zone, a low pressure weather zone near the equator that is associated with heavy rainfall.  Because winds are not static, the convergence zones fluctuate seasonally, moving further north or south depending on the time of year.

For scientists, one of the most challenging aspects of studying the accumulation of plastic in the gyre is finding it, because the Subtropical Convergence Zone moves around.  When scientists target the area with the highest accumulation of plastic, they are looking for this moving target.

For more information go to check out these sites:
http://www.seaplexscience.com
http://www.projectkaisei.org
http://kaisei.blipback.com

Thank you to our sponsor, Samy's Camera

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