Ocean Currents and Coastal Temperatures



Ocean Currents and Coastal Temperatures

Objective:

Relate the role of ocean surface currents to climate.

Background:

Warm and cold ocean currents can affect the climate of an area along the coast if the winds blow in from the ocean. Warm ocean currents heat the air above the water and carry the warm air to the land, increasing the temperature of the coastal region. The same is true for cold ocean currents, except that they carry cooler air to the land and lower the temperatures of the coastal region.

This effect can be seen in two cities at the same latitudes, but along different coastlines. For example, cities along the west coast of the United States are affected by a cool ocean current that carries cool air toward the California coast. Along the east coast, the Gulf Stream brings warm air toward the coast, which helps maintain warmer temperatures along the coast. Areas that are “landlocked” receive the sun’s energy directly, based on latitude, but do not have the moderating effects of the ocean currents and the air they bring with them.

Set Up:

Students will chart the temperatures of three cities at approximately the same latitude. They will develop a hypothesis that explains the cities’ temperature differences, plot them on the ocean current map and rethink their hypothesis.

Students should use their “Color the Ocean Current” map to help identify major warm and cold ocean currents that may affect their cities. For students not having an ocean current map, an ocean current map is attached. This map is in color, and students will have to label the currents as cool or warm.

Extension:

To test student understanding, give them the global temperature section of the newspaper. Have them find pairs of coastal cities at about the same latitude but on opposite sides of the same continent (not necessarily North America). See if they can predict the type of current off each coastline by using temperature data alone.

Alternatively, have students look at the map that shows warm and cold currents (attached). They can use this to try to predict the climate of coastal areas throughout the world. Have them compare their predictions to weather and climate data from newspaper, the Internet, or an almanac.

Ocean Currents and Coastal Temperatures

Background:

Warm and cold ocean currents can affect the climate of an area along the coast if the winds blow in from the ocean. Warm ocean currents heat the air above the water and carry the warm air to the land, increasing the temperature of the coastal region. The same is true for cold ocean currents, except that they carry cooler air to the land and lower the temperatures of the coastal region.

This effect can be seen in two cities at the same latitudes, but along different coastlines. For example, cities along the west coast of the United States are affected by a cool ocean current that carries cool air toward the California coast. Along the east coast, the Gulf Stream brings warm air toward the coast, which helps maintain warmer temperatures along the coast. Areas that are “landlocked” receive the sun’s energy directly, based on latitude, but do not have the moderating effects of the ocean currents and the air they bring with them.

Problem: Why do cities at about the same latitude have different temperatures?

1. Select one of the groups, A, B or C, of three cities from the table below. Notice that the three cities are at about the same latitude on the map. Two of the cities lie along different coastlines and one is landlocked (not along a coast).

2. Develop a hypothesis that responds to the problem question.

|Group |City number on map |City |Low temperature |High temperature |North Latitude |

| | | |Jan oC |July oC | |

|A |1 |Seattle |7 |22 |47.5 |

| |5 |Belfast |6 |18 |54.0 |

| |6 |Moscow |-9 |23 |56.0 |

C |7 |Tokoyo |8 |28 |35.0 | | |8 |Kabul |2 |31 |35.0 | | |9 |Los Angeles |18 |27 |34.0 | |

Group of cities selected: (circle one) A B C

City 1: Name: _______________ Latitude: ________

City 2: Name: ______________ Latitude: ________

City 3: Name: _______________ Latitude: ________



Hypothesis: (Remember the problem: Why do cities at about the same latitude have different temperatures?)

____________________________________________________________________

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Analysis:

1. Locate the approximate location of the three cities on the ocean surface current map.

2. Use the location of the cities and a surface ocean current map to determine if warm or cool water currents flow off each coast next to the coastal cities. Sketch in the current(s) on the map above. Use red and blue map pencils to show warm and cool currents.

3. Think about why the three cities are at about the same latitude, but have such different temperatures. Remember that because of their latitude, they are receiving similar amounts of energy from the sun.

4. Answer the following questions.

a. Name the ocean currents that might affect the coastal cities you selected.

b. Identify each current a being warm or cool.

c. Identify the direction each current flows.

d. Determine how the current will affect the coastal city.

e. Explain why the “landlocked” city’s temperatures are different from the coastal cities.

5. Rethink your hypothesis and develop an explanation for the differences in temperatures for the three cities. Write your explanation in the space below.

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Materials:

• map of ocean currents

• map of US

• map pencils

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