Currents and Gyres – Plastics and Global Circulation

Lesson

This lesson was co-created by science educator Neil Leonard and is part of the NGSS MS-ESS 3-3 Human Impact – “Plastic Ocean” Standards Alignment Guide.

Purpose and Context

What are currents? 

Currents are important features in the global circulation patterns in Earth’s Ocean. They transport heat, energy, animals, and nutrients through the oceans and impacting regional climates and ecosystems. Currents are formed by systems of interacting forces, including energy from the sun, atmospheric circulation and wind, and the rotation of the earth.  

Currents actually occur in the air, too! Wind can be thought of as a current of air, moving between areas of different pressure. Currents can also occur in electrical systems as the flow of electrons between areas of different charge.  

In general, we can think of currents as movement or flow driven by a differential in temperature, pressure, or charge.    

Another example is a convection current. These are currents formed by the rising of hot air or water, or the sinking of cold air or water.  

Currents in our atmosphere: Atmospheric cells 

The Planet Earth is spinning rapidly as we orbit the sun. As the earth spins, light from the sun heats our atmosphere. More light hits the land, water, and air near the equator as compared to near the poles. This uneven distribution of heat energy drives the movement of air in our atmosphere, and the movement of water in the oceans. These forces and others create complex patterns that determine regional climates. Scientists have learned about these complex patterns by studying changes in our ocean and air circulation with many measuring devices, like satellites, weather stations, weather balloons, and buoys in the ocean that collect information on temperature, pressure, humidity, salinity, etc. 

Scientists have even learned about how the ocean moves by studying how plastic pollution moves and collects in the ocean.  

Plastic debris floating on currents: 

During his 1997 voyage from Hawaii to California, Capt. Moore took a path usually avoided by sailors, and went straight through the doldrums, where sailors would often get stuck due to the lack of wind! With a motor on board, they were safe, and journeyed through. They started to see something weird floating in the water – small flecks of something. After scooping some of it out, they found out it was plastic. Why was plastic accumulating out in the middle of the vast ocean?!  

In his book Plastic Ocean, Capt. Moore recounts how he worked with other researchers to use plastics and other debris as clues for learning how the ocean moves (how ironic, right!). Curtis Ebbesmeyer, one of these researchers, is known for his investigation of the Friendly Floatees, thousands of bath toys spilled out of a shipping container that fell overboard. As an oceanographer, he was able to deduce information about how the ocean currents travel by where and when the Friendly Floatees were found washed up on shore.  

Photo: Oceanographer Curtis Ebbesmeyer with flotsam (including some Friendly Floatees) that he observes to monitor ocean currents. Original photo: Rick Rickman Photo re-work: Liberal Freemason at German Wikipedia – http://vos.noaa.gov/MWL/dec2001.pdf

Instructions

Guide students through an introduction of the forces impacting the movement of air and water on the planet, the formation of gyres, and how they accumulate plastics using the presentation slides, student handout, and included simulations.  

See the notes below each slide for more information. 

Associated Standards

Next Generation Science Standards

MS-ESS2-6. Develop and use a model to describe how unequal heating and rotation of the Earth cause patterns of atmospheric and oceanic circulation that determine regional climates.

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