What Causes Ocean Currents?
Water moves continuously through the ocean in huge rivers called currents. Currents may flow on the surface of the ocean, where they are shallow, or they may flow far below the surface, where they are deeper. Ocean currents are set in motion by the wind. The rotation of the earth moves them clockwise in the Northern Hemisphere a
Ocean currents result from two processes – the action of wind on the surface of the water, and from variation in water temperature that causes movement- a process known as convection. Convection occurs because the oceanic waters heat up becoming less dense. This water moves above the cooler water, and give off its heat to the surrounding environment. As it cools, it begins to sink, and the process begins again. Convection results in the continual circulation of ocean water on a global scale. There are many factors that determine the strength of a current, as well as the route it will follow. Winds have the most important influence on the flow of currents, but tides, precipitation, evaporation rates, shape of the ocean floor, and inflow from rivers and adjacent seas are also important. The major currents in the North Atlantic Ocean flow along the eastern North American coast from the Gulf of Mexico to the tip of Labrador.
What impact do they have on Earth’s environment? How have they influenced human history? Students gain fascinating insights into our ocean planet through these innovative activities. They learn how wind, temperature, salinity, and density set water into motion, and they make an “in-depth” investigation of the key physical science concept of density. They model how pollution dumped in one location can spread throughout the ocean. Learning is placed in a real-world context as students predict and analyze routes taken by shipwrecked sailors, the 1990 Nike shoe spill, the raft Kon Tiki, and other voyages. In “Message in a Bottle,” students create stories to show what they’ve learned over the course of the unit. This GEMS guide adapts activities developed by the Marine Activities, Resources & Education (MARE) program of the Lawrence Hall of Science. It connects swimmingly with the marine-oriented GEMS guides Only One Ocean and On Sandy Shores. From the forward by E.C. Haderlie, Distinguishe
