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Grade 10 Academic Science – Climate Change Energy Transfer in Air and Water Water has a remarkable ability to absorb and store thermal energy. Thus, water is a HEAT SINK. How is climate impacted? When air is warmer than the ocean surface, the ocean ABSORBS thermal energy FROM the air. Likewise when air is cooler than the ocean surface, the ocean RELEASES thermal energy TO the air. As a result, the climates of regions close to oceans and large bodies of water (e.g., Great Lakes) tend to have more moderate climates (i.e., mild winter and cool summers). When thermal energy is transferred, it always moves from a WARM object or region to a COOLER object or region. There are four ways to move or transfer thermal energy: Radiation (e.g., electromagnetic waves) Conduction (e.g., through contact) Advection (e.g., horizontally through a liquid or gas) Convection (e.g., vertically through a liquid or gas) Most of the energy transfer in air and water occurs via CONVECTION CURRENTS…the circular movement of matter within a fluid or gas caused by the rising of warm fluid as cool fluid sinks. The picture shows air rising and falling in a convection current pattern during day and night times. Energy Transfer in the Atmosphere Warm air is less dense while cold air is more dense Air at the Earth’s equator heats up quickly and becomes less dense. Cold, dense air higher in the atmosphere drops below the warm air and pushes the warm air up into the atmosphere. This is an area of LOW PRESSURE. The warm air spreads out towards the North and South Poles, and at the higher altitude, begins to cool and become dense. As cooler air, it sinks backs towards the surface of the Earth. This is an area of HIGH PRESSURE This movement of cool and warm air creates a convection current in the atmosphere. As shown in the picture, many convection cells form around the Earth. The cells cause prevailing winds and the movement of thermal energy towards the North and South Poles. The movement of winds impact climate in a region. As wind moves over water, it picks up water vapour via evaporation. When the wind reaches land, the water condenses and precipitation occurs. Energy Transfer in the Oceans Ocean currents also transfer thermal energy and affect climate. Oceans currents are driven by three factors: (1) prevailing winds that move warm water on the surface, and (2) convection and (3) uneven concentrations of salts in ocean waters that move cold subsurface waters. The movement of water based on differences in temperature and salt concentration is called THERMOHALINE CIRCULATION. It moves water and thermal energy from the equator to the poles. Warm surface water moves to the poles and get colder. It also becomes more salty as some water evaporates. Now cold and salty, the water sinks to the ocean floor. Warm water flows in to replace it and a current is formed. Cold ocean currents cool the air above them. The cool air then cools nearby land. Since cool air cannot hold moisture, the climate is cool and dry. Warm water heats the air above it. Warm air carries moisture. The climate is warm and wet. When warm and cold ocean currents meet, fog forms. Make an ocean current Purpose: To observe convection currents Materials Two colours of food colouring Fish tank or large clear glass container Water Heat Lamp or Heating Pad Sealed bag of ice cubes (small reusable plastic bag) 500 mL beaker 500 mL beaker (same) for hot water OR plastic bag / container for hot water Tongs and insulated gloves (for handling hot water) Methods Fill the container 1/3 full of water Plug in the heat lamp, turn on and shine at one end of the container OR heat water over heat pad in beaker until nearly boiling Lower the bag of ice cubes into the other end of the container Transfer hot water to bag (optional – you can leave the water in the beaker if water level in fish tank is NOT higher than top of beaker) Lower hot water into fish tank Add one colour of food colouring to the water at the end of the container beside the hot water Add the other colour of food colouring to the water next to the ice cubes Record your observations Explain your observation in a lab report.