Chapter: Oceans Table of Contents Section 3: WavesWaves Section 1: Ocean Water Section 2: Ocean Currents and ClimateOcean Currents and Climate Section 4: Life in the OceansLife in the Oceans
A. Surface Currents 1. Ocean water never stands still. Currents move the water from place to place constantly. Ocean Currents and Climate 2 2
A. Surface Currents 2. They exist both at the ocean’s surface and in deeper water. Ocean Currents and Climate 2 2
B. Causes of Surface Currents 1. surface currents are powered by wind and usually move only the upper few hundred meters of seawater. 2. Because of Earth’s rotation, ocean currents do not move in straight lines. 3. Earth’s rotation causes surface ocean currents in the northern hemisphere to curve to the right and surface ocean currents in the southern hemisphere to curve to the left. Ocean Currents and Climate 2 2
C. The Gulf Stream 1. One of the most important currents for sailing east across the North Atlantic Ocean is the Gulf Stream. 2. The Gulf Stream flows from Florida northeastward toward North Carolina. There it curves toward the east and becomes slower and broader. Ocean Currents and Climate 2 2
C. The Gulf Stream 3. Currents on eastern coasts of continents, like the Gulf Stream, are usually warm, while currents on western coasts of continents are usually cold. Ocean Currents and Climate 2 2
D. Climate 1. Locate Iceland on the map. 2. Based on its location and its name, you might expect it to have a cold climate. Ocean Currents and Climate 2 2
D. Climate 4. The current’s warm water heats the surrounding air and keeps Iceland’s climate mild and its harbors ice free year-round. Ocean Currents and Climate 2 2 3. However, the Gulf Stream flows past Iceland.
E. Cold Surface Currents Ocean Currents and Climate 2 2 1. Find the California Current off the west coast of North America and the Peru Current along the west coast of South America. It carries cold water from polar regions toward the equator.
E. Cold Surface Currents 3. San Francisco has cool summers and many foggy days because of the California Currents. Ocean Currents and Climate 2 2 2. Cold surface current affect the climate of coastal cities.
F. Density Currents 1.A density current forms when a mass of dense seawater sinks beneath less dense seawater. 2.Seawater becomes more dense when it gets colder or becomes more salty. 3.Changes in temperature and salinity work together to create density currents. A density current moves very slowly. Ocean Currents and Climate 2 2
G. Cold and Salty Water 1. An important density current that affects many regions of Earth’s oceans begins north of Iceland. 2. When water freezes, dissolved salts are left behind in the unfrozen water which is very dense because it is cold and salty. Ocean Currents and Climate 2 2 3. It sinks and slowly flows along the ocean floor toward the southern Atlantic Ocean.
G. Cold and Salty Water 4. As the water is sinking near Iceland, warm surface water of the Gulf Stream, shown in red, moves northward from the equator to replace it. Ocean Currents and Climate 2 2
H. Density Currents and Climate Change 1. If Earth’s temperature rose enough, ice couldn’t easily form near the polar regions. Ocean Currents and Climate 2 2 2. Freshwater from melting glaciers on land also could reduce the salinity of the ocean water.
H. Density Currents and Climate Change Ocean Currents and Climate 2 2 3. The density currents would weaken or stop. If density currents stopped flowing southward, warm equatorial surface water would no longer flow northward. 4. Earth could face drastic climate shifts, including changing rainfall patterns and temperatures.
I. Upwelling 1. An upwelling is a current in the ocean that brings deep, cold water to the ocean surface. Ocean Currents and Climate 2 2 2. This occurs along some coasts where winds cause surface water to move away from the land.
I. Upwelling Ocean Currents and Climate 2 2 3. Notice that when surface water is pushed away from the coast, deep water rises to the surface to take its place. 4. This cold, deep water continually replaces the surface water that is pushed away from the coast.
I. Upwelling Ocean Currents and Climate 2 2 5. The cold water is full of nutrients from dead, decayed organisms. Tiny marine organisms thrive in these nutrient- rich areas, which, in turn, attract many fish. As a result, areas of upwelling are important fishing grounds because fish are attracted to the areas to eat the organisms.
J. El Niño 1. During an El Niño (el NEEN yoh) event, the winds blowing water from the coast of Peru slow down. The Eastern Pacific Ocean becomes warmer, and upwelling is reduced or stops. Ocean Currents and Climate 2 2 2.Without nutrients provided by upwelling, fish and other organisms cannot find food. Thus, the rich fishing grounds off of Peru are disrupted.
Section Check 2 2 Question 1 Which way do currents rotate in the southern hemisphere?
Section Check 2 2 Question 2 Explain how the climate of different regions is affected by ocean currents.
Section Check 2 2 Question 3 What type of current exists in the Mediterranean Sea? A. cold surface current B. density current C. surface current D. upwelling
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