Miss Nelson SCIENCE ~ CHAPTER 9 CLIMATE

Currents and Climate SECTION 2

Have you ever heard a story about someone finding a message in a bottle that was thrown into the ocean? How did the bottle travel all the way to them? ANTICIPATORY SET

S 6.4.d – Students know that convection currents distribute heat in the atmosphere and oceans S 6.4.e – Students know differences in pressure, heat, air movement, and humidity result in change in weather STANDARDS

What causes surface currents and deep currents? What effects do they have? THE BIG IDEA

 El Niño –A climate that occurs every two to seven years in the Pacific Ocean, during which winds shift and push warm water toward South America  La Niña – A climate in the eastern Pacific Ocean in which surface waters are colder than normal  Salinity – The total amount of dissolved salts in water  Upwelling – The movement of cold water upward from the deep ocean that is caused by wind  Coriolis effect – The effect of Earth’s rotation on the direction of winds and currents KEY TERMS

Read Currents and Climate on page 356 of your textbook CURRENTS AND CLIMATE

Surface currents (which affect water to a depth of several hundred meters) are driven mainly by winds SURFACE CURRENTS

Most of the currents flow east or west, and then double back to complete a circle View Figure 8 on pages 457 of your textbook SURFACE CURRENTS

 Winds are caused by differences in air pressure  Differences in air pressure are the result of the unequal heating of the atmosphere by the sun  The sun’s radiation (of heat) is the ultimate source of energy that powers global winds and surface currents in the ocean SURFACE CURRENTS

 Global winds are not the only factors that influence surface currents  Continents block and redirect the flow of currents  Coriolis effect also influences surface currents  Causes global winds to curve as a result of Earth’s rotation CORIOLIS EFFECT

A surface current warms or cools the air above it, influencing the climate of the land near the coast EFFECTS ON CLIMATE

Warm-water currents  Winds pick up moisture as they blow across Cold-water currents  Cool the air above them  Cold air holds less moisture – these currents tend to bring cool, dry weather to lands in their path EFFECTS ON CLIMATE

Read Surface Currents on pages 357 – 358 of your textbook SURFACE CURRENTS

 El Niño and La Niña are short-term changes in the tropical Pacific Ocean cause by changes in ocean surface currents and prevailing winds  El Niño is a warm-water event that disrupts the cold ocean currents along the western coast of South America  Effects weather patterns around the world  La Niña is the opposite – when surface waters in the Pacific are colder than normal  Brings colder than normal winters and greater precipitation  Causes hurricane activity in the western Atlantic EL NIÑO AND LA NIÑA

Read El Niño and La Niña on page 359 of your textbook EL NIÑO AND LA NIÑA

Deep currents are caused by differences in the density of ocean water DEEP CURRENTS

The density of ocean water depends on its temperature and its salinity OCEAN WATER DENSITY

View Figure 11 on page 360 of your textbook OCEAN WATER DENSITY

Deep currents move and mix water around the world They carry water from the poles toward the equator A GLOBAL CONVEYER BELT

 Deep currents flow SLOWLY  May take as long as 1,000 years to flow from the pole to the equator and back again A GLOBAL CONVEYER BELT

Read Deep Currents on page 360 of your textbook DEEP CURRENTS

Upwelling brings up tiny ocean organisms, minerals, and other nutrients from the deeper layers of the water UPWELLING

 In most parts of the ocean surface waters do not usually mix with deep ocean waters  Mixing sometimes occurs as winds blow away the warm surface water and cold water rises up to replace it  Without this motion the surface waters of the open ocean would be very scarce in nutrients UPWELLING

 Upwelling occurs in the Pacific Ocean off the west coasts of North and South America  The arrival of El Niño prevents upwelling from occurring  Without the nutrients brought by upwelling, fish die or go elsewhere to find food UPWELLING

Read Upwelling on page 361 of your textbook UPWELLING

Surface currents are mainly driven by what? What causes deep currents? CHECK FOR UNDERSTANDING

Surface currents are mainly driven by what? Surface currents are driven mainly by winds. What causes deep currents? Deep currents are caused by differences in the density of ocean water. CHECK FOR UNDERSTANDING

Complete the Modeling, Guided Practice, and Independent Practice Sections of your Climate 9-2 Worksheet. MODELING / GUIDED / INDEPENDENT