|Earth and Space Science||Oceanography 5M3.00||Process of Science||Collecting Data 1.3 a|
Sponsored by the National Science Foundation
CONTENT STANDARD: Earth and Space Science
CONTENT TOPIC: Oceanography
CONCEPT: The topography of the ocean floor is in constant change.
CONTENT OBJECTIVE: 5M3.00 To understand relationships among oceans, weather, and climate
INSTRUCTIONAL OBJECTIVES: The learner will:
TN COMPONENT OF SCIENCE: Process of Science
BENCHMARK: Information gathered through the use of instrumentation and/or experimentation is to be managed so that data can be easily retrieved.
The transfer of heat by currents of air is called convection. A transfer of heat by currents of water is also convection. Particles of warm air or warm water move in convection currents from one place to another.
When air becomes warm, it begins to move in a convection current. The warm air expands. It expands and moves upward. Heavier, cold air replaces the warm air. Many homes are heated with convection currents. Hot air flows into the room from a vent near the floor. The hot air rises and warms the room. Cold air drops to the floor.
Convection also causes the breeze at the seashore. On a warm summer day, the land gets warmer than the ocean. During the afternoon, the land gives up some of its heat to the air. The hot air over the land rises. Cool air from the ocean moves in across the land. This cool air is a sea breeze.
On a clear night, the land cools off faster than the ocean. The air over the land becomes cooler than the air over the ocean. The cooler land air moves out to sea. This is a land breeze.
At the seashore you will note these changes in the direction of the wind. A sea breeze moves toward the land from the sea. A land breeze moves from the land toward the sea.
The convection of heat can be observed in the oceans. Ocean water near the equator is heated by the sun. The warm water is lighter in weight than cold water farther north and south. Currents of warm water moving north and south are set up by this difference in weight. In the Atlantic Ocean, such a convection current is the Gulf Stream.
The Gulf Stream follows the contours of the North American continent to the area of Cape Hatteras. The four capes of the southern Atlantic coast of the United States have been shaped by the section of the Gulf Stream as it moves north. The capes are Cape Kennedy, Cape Fear, Cape Lookout, and Cape Hatteras.
Above Cape Hatteras, the Gulf Stream leaves the continental shelf. It becomes a narrow current. Meanwhile, the Labrador Current moves down from the north. It is a cold current. The cold Labrador Current pushes the warm Gulf Stream to the east. At times there is a twenty degree difference between the temperature of the Labrador Current and the Gulf Stream. The waters in each current run past each other, side by side. The Labrador Current has a green color to its water. The Gulf Stream is blue.
As the Gulf Stream moves east across the Atlantic Ocean, it branches off into three different directions. One branch of the Gulf Stream goes south to the Sargasso Sea. Another flows into the Norwegian Sea. A third branch continues eastward to warm the coast of Europe.
The Gulf Stream affects the climate in Europe. The temperature in England, for example, is higher than in most countries of the same latitude. The Gulf Stream gives England its extra warmth.
Ocean currents are produced by many different things. Currents are made by the gravitational pull of the moon and sun, the prevailing winds blowing on the ocean surface and the unequal heating of the water by the rays of the sun. The ocean currents are also affected by the rotation of the earth. The general movement of the currents is clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
Holding your finger over the top of the bottle, place it upright in the fish bowl of cold water. Remove your finger and watch the warm colored water rise and swirl in currents.
The temperature of ocean water affects the climate of nearby land. Land is warmed quickly by the sun. Ocean water is not warmed as quickly. Air above the water is cooler than air above the land. The land is cooled as the cool air over the ocean moves inland. Ocean water stays warm for a long time, once it is heated. The air above the water stays warm also. In winter, warm air over the ocean moves inland. The air keeps the land warm.
The ocean is also part of the water cycle. The sun's heat evaporates ocean water. Water vapor rises and forms clouds. Winds carry clouds over the land. Rain and snow fall from the clouds affecting climate and weather.
This is the time this file has been accessed since 08/01/97.
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