Surface Ocean Currents

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-ESS2-4

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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NGSS.MS-ESS2-6

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

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

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-ESS2-4

NGSS.MS-ESS2-6

These currents are a form of convection in the ocean. What is one effect of this convection?

• Warm water on the ocean's surface stays on the surface.

• The ocean constantly becomes colder as warm water is cooled.

• Water from the ocean cools the atmosphere.

• Water continually circulates throughout Earth's oceans.

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NGSS.MS-ESS2-4

NGSS.MS-ESS2-6

The image shows part of an ocean current in the Atlantic Ocean. The blue line represents the motion of deep, cool water. The red line represents the motion of warm surface water. One factor that affects ocean currents is the concentration of salt in the water. How can the saltiness of the water cause the surface water to sink, as shown above?

• When ice melts, it makes the surface water more salty.

• When cold water rises to the surface, it loses salt.

• When some of the surface water freezes, the remaining water becomes saltier.

• When the surface water is heated by the Sun, it dissolves more salt.

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NGSS.MS-ESS2-6

Why does the cycle of El Niño affect the weather across the Pacific Ocean?

• Energy from the warm water creates winds that blow across the ocean.

• Additional salt in the ocean changes the rate at which water evaporates.

• The ocean currents change, transferring heat around the ocean differently.

• Temperature differences in the ocean prevent the convection of ocean water.

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NGSS.MS-ESS2-6

The ocean contains currents as a result of uneven heating and uneven salt concentration. These currents exist both on the ocean surface and deep in the ocean.

Which diagram best represents the currents in the ocean?

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NGSS.MS-ESS2-6