Bellringer 1.What biome has trees that lose their leaves in the fall? 2.What do you call organisms in a food chain that produce their own food? 3.Give an abiotic factor found in the tropical rain forest. One that affects the organisms that live there. 4.What is the difference between a food chain and a food web?

Ocean Currents

What is a current? An ocean current is a large stream of moving water that flows through the ocean.

Surface Currents Move in the upper few hundred meters of the water SC Warms or cools the air above it, influencing the climate of land near the coast. Controlled by 3 things: 1.Global winds 2.Coriolis Effect 3.Continental Deflection (Position of continents)

1. Global Winds Different winds cause currents to flow in different directions Near the equator – winds blow ocean water east to west Closer to the poles – ocean water is blown west to east Merchant boats use winds to help them travel more quickly.

Ben Franklin and the Gulf Stream

2. The Coriolis Effect Earth ’ s rotation causes wind and surface currents to move in curved paths Imagine trying to roll a ball straight across a turning merry-go-round… the spinning causes the path of the ball to curve. Northern Hemisphere: move clockwise Southern Hemisphere: move counterclockwise

3. Continental Deflection If there were no continents, currents would move in uniform patterns BUT…as currents “ bump into ” continents, they change direction When surface currents meet continents, the currents deflect, or change directions.

Temperature All three factors – winds, Coriolis Effect, and continents – Work together to form a pattern of surface currents on Earth But the current is also affected by the temperature of the water in which it forms Warm water currents – start near equator Cold water currents – start near poles

Gulf Stream Powerful surface current in the Atlantic. 30km wide and 300m deep Carries a volume of water 100x greater than Mississippi River. 25x more water than all rivers in the world From the Gulf of Mexico to Caribbean Sea and up the north coast of the U.S.

Before much was known about ocean currents, sailors would stop their boats for the night only to wake up extremely confused when they found themselves miles away from where they stopped. The Gulf Stream is one current that presented these ancient mariners with many challenges. This especially powerful current is almost 1 mile (1.6) kilometers deep and can move up to 26 billion gallons of water a second. That's more than the flow of the Amazon River! The current has caused so many shipwrecks around Cape Hatteras, a piece of land that juts out sharply from the east coast of North Carolina, that the area is called the graveyard of the Atlantic.

Exit Ticket Tell me three things that you learned today Tell me two things that you found interesting. Give me one that thing (word or statement) needs to be explained to help you understand it better.

Deep Currents Currents far below surface Not controlled by wind Caused by differences in density and salinity Lowering the temperature and increasing the salinity increases the density of water Where there is denser water – currents begin Move slower and may take as long as 1,000 yrs to make a round trip Carry cold water from the poles back to the equator along the ocean floor.

How Deep Currents form Warm surface currents flow toward poles, water cools, becomes denser and sinks (becoming deep currents)

Deep water currents form in parts of the ocean where density increases. The warm less-dense water in surface currents cools and becomes the colder, denser water in deep currents

How deep water currents form: Decreasing temperature Increasing salinity through freezing Increasing salinity through evaporation