1. Water and the Atmosphere – Chapter 2 Lesson 3
Currents and Climate
Water and the Atmosphere – Chapter 2 Lesson 3

2. Ducky Overboard
What happens when a ship loses its cargo at sea? Is it gone forever? You might think so.
One ship traveling from Hong Kong to Tacoma, Washington, lost 29,000 plastic toys.
They fell overboard in a storm and were considered lost at sea.
But when hundreds of the toys began washing up on distant shores, scientists got excited.  
One way scientists study ocean currents is by releasing empty bottles into the ocean.
But of 500 to 1,000 bottles released, scientists might only recover 10. That doesn’t give them much data.
The large number of floating toys could give scientists better data from more data points.  
The first toys were spotted off the coast of Alaska. Then beachcombers began finding them in Canada, in Washington, and even as far away as Scotland.
Why was the plastic toy spill so helpful to scientists studying ocean currents?
Have you ever found objects on the beach? What data would scientists need from you for their research?

4. El Niño
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What prevents the cooler ocean water from rising to the surface during an El Niño event?
Based on what you've learned, name two continents that are less likely to be impacted by an El Niño event. Explain your answer.

5. What Causes Deep Currents? Summary
Deep currents are caused by differences in the density of ocean water.
When a surface current moves toward the poles, its water temperature decreases and its salinity increases.
The water becomes denser and sinks.
Then, the cold water flows back along the ocean floor as a deep current. 
Deep currents move and mix water around the world.
They carry cold water from the poles toward the equator.
The pattern of ocean currents looks like a conveyor belt, moving water between the oceans.
This pattern of ocean currents is called the thermohaline circulation.
How does the density of ocean water affect deep currents?

6. What Causes Surface Currents? Summary
A current is a large stream of moving water that flows through the oceans.
Unlike waves, currents carry water from one place to another.
Surface currents affect water to a depth of several hundred meters.
They are driven mainly by winds.

8. What Causes Surface Currents?
As Earth rotates, the paths of winds and currents curve.
This effect of Earth's rotation on the direction of winds and currents is called the Coriolis effect.
The Gulf Stream is the largest and most powerful surface current in the North Atlantic Ocean.
It has a warming effect on the climate of nearby land areas.
Climate is the pattern of temperature and precipitation typical of an area over a long period of time.
A surface current warms or cools the air above it.
This affects the climate of land near the coast.

10. What Causes Surface Currents?
Changes in wind patterns and currents can have a major impact on the oceans and neighboring land.
One example of such changes is El Niño, a climate event that occurs every two to seven years in the Pacific Ocean.
When El Niño occurs, unusual wind patterns cause a vast sheet of warm water to move east toward South America.
When surface waters in the eastern Pacific are colder than normal, a climate event known as La Niña occurs.
Compare and Contrast Compare and contrast the effects of warm and cold currents on climate.