Evaporations and Ocean Currents

The Earth's oceans are generally warmer near the equator and cooler near the poles. Currents in the water near the surface circulate the water. Some of these currents are shown in the image below. Warm currents are shown in red. Cool currents are shown in blue.

Which of the following best describes what the pictured currents do?

• carry warm water away from the poles

• carry cool water toward the poles

• carry warm water toward the equator

• carry warm water away from the equator

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NGSS.MS-ESS2-6

Warm air and water both tend to rise while cooler air and water sink. When different parts of the oceans are heated unevenly, this causes the water to

• mix together in the water cycle.

• move in convection currents.

• stay in the same place.

• form a tsunami.

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Water is cooler near the poles and warmer near the equator. Movement of cooler and warmer water from these regions moderates the global climate.

Which of the following describes the movement of water between the poles and the equator?

• ocean currents

• gravity

• evaporation

• tides

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NGSS.MS-ESS2-6

A process known as upwelling often occurs along ocean coasts. In this process, warm water at the surface is driven out to sea by blowing winds. As the warm water moves out to sea, what most likely happens to the cold water beneath it?

• It condenses into ice.

• It sinks closer to the ocean floor.

• It rises to the surface to replace the warm water.

• It is driven out to sea by the warm water.

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NGSS.MS-ESS2-6

A student puts water in a long glass tank to make a model of ocean currents. He heats the left side of the tank and cools the right side. This heating and cooling produces a current of water in the tank.

Which diagram correctly shows the flow of the water?

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The currents of the Earth's oceans are caused by

• global winds and differences in temperature and salinity.

• marine organisms and volcanic eruptions.

• waves and earthquakes along tectonic plate boundaries.

• disturbances by submarines and large ships.

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NGSS.MS-ESS2-6

A student wants to make a model of ocean currents. She divides a long glass tank in half, as shown below. She puts fresh water in one side and salt water in the other side.

Next, the student removes the barrier between the two sides.

Which diagram correctly shows the flow of the water when the barrier is removed?

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NGSS.MS-ESS2-4

Which is true?

• The ocean has no effect on the temperature on the land.

• All ocean water is the same temperature.

• Ocean water does not move between locations.

• Ocean currents affect temperatures on land.

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NGSS.MS-ESS2-6

Water in ocean currents can descend when it becomes colder and saltier than the surrounding water. If water descends to the bottom of the ocean, then other water must rise to the top. What causes water to rise to the top of the ocean?

• It becomes less dense than the surrounding water.

• It is forced upward by underwater mountain ranges.

• It is brought upward by organisms that live in the ocean.

• It cools down and dissolves additional salt.

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NGSS.MS-ESS2-6

The ocean's currents are driven by differences in temperature and density. Different masses of water are warmer and less dense than other masses. This water tends to move along the ocean's surface in surface currents. Colder masses and more dense masses of water tend to sink and move along the ocean floor in deep-water currents.

As shown in the diagram, at several locations warm, less dense water cools, becomes more dense and falls to the ocean floor. At other locations, cold, dense water warms, becomes less dense and rises back to the surface.

This cycling of ocean water along currents is an example of _______.

• conduction

• absorption

• convection

• radiation

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NGSS.MS-ESS2-6