Lesson 5 Thermal Energy and Climate

  Thermal Energy and the Hydrosphere

D5.13 Convection current in the ocean

The hydrosphere helps to transfer thermal energy from areas where there is lots of thermal energy to areas where there is less. A large part of this transfer occurs through the currents in the ocean. Just like wind, the ocean currents are caused by convection.

As ocean water moves north, it cools and freezes.  When sea ice forms, the salt is left out of the ice, making ocean water more salty.  This cold, salty water is more dense, so it sinks.  This can be thought of as the pump that drives ocean currents.

Cold water sinks and tends to more towards the equator.  Warm, less dense water moves on the surface to replace the water that sunk. As it moves towards the poles, it releases thermal energy into its surroundings, affecting the climate of those places. The ocean can move a lots of heat because it has a high specific heat capacity.  And little energy from the ocean is required to change air temperature because it has a high specific heat capacity.

Surface currents are then affected by wind patterns and the Coriolis effect.

When thinking about thermal energy being transferred in the hydrosphere, you will want to remember the affects the specific heat capacity, heat of fusion, and heat of vaporization have on climate.

Surface Currents

These surface currents in the oceans are caused by the winds we studied, such as the trade winds, on the previous page.  The surface currents do not follow the exact path of these winds that cause them, because the continents get in the way. Large land masses get in the way of the currents and tend to cause the current to circle back on it. You can see this effect in image D5.14. Notice how the currents near the equator flow toward the equator and toward the west—the same way as the trade winds. The currents between the equator and the poles tend to flow toward the east before they run into a land mass and turn around—just like the westerly winds. The currents near the poles flow to the west—just like the easterly winds.

D5.14 Ocean currents

Coriolis Effect

D5.15 Clockwise and counterclockwise currents

The Coriolis effect also affects these currents. The currents in the Northern Hemisphere are pushed in a clockwise direction, while the currents in the Southern Hemisphere are pushed in a counterclockwise direction. These factors cause some costal locations to get a continuous current of warm water, such as Victoria, British Columbia, while others get a continuous current of cold water, such as Labrador, New Foundland. This causes Victoria’s climate to be warmer than it should be when considering its location on Earth. It also causes Labrador to have a cooler climate. The location of these two cities still means that they have less variation in temperature when compared to an inland community at the same latitude, even if it is a warmer or cooler temperature, since they are near a large body of water.

  Digging Deeper

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D5.16 Water spinning as a toilet is flushed

Does water spin differently down a drain depending on what hemisphere you are in? The answer to this question has sparked much debate over the years. Some are adamant that the water does spin in different directions depending on the hemisphere; while others say that the Coriolis effect would have little to no effect and that any differences seen are due to the shape of the basin. Go to the following link to find out the answer. https://www.scientificamerican.com/article/can-somebody-finally-sett/

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  Practice Questions

1. Complete the following chart using your readings and notes.
   
   

   Factor	Affect on Ocean Current	How It Affects Climate or Thermal Energy Transfer
   convection
   Coriolis effect
   continents
   specific heat capacity	n/a
   heat of vaporization	n/a

   
   
   Check your answer
   

   Factor	Affect on Ocean Current	How It Affects Climate or Thermal Energy Transfer
   convection	The denser cool water sinks as the less dense warm water rises, creating a current that runs from warm areas to cool areas and back.	The water absorbs thermal energy in the warm area to release it in the cooler areas.
   trade winds	These form the surface currents near the equator.	The water absorbs thermal energy and starts to move it away from the equator.
   westerlies	These form the surface currents between 30˚ and 60˚ in each hemisphere.	These bring warm water from the equator to areas farther away from the equator. They bring thermal energy to places with less thermal energy.
   easterlies	These form the surface currents at each of the poles.	These cause the cool water to start to move back toward the equator to absorb more thermal energy to bring toward the poles.
   Coriolis effect	These cause currents in the Northern Hemisphere to flow clockwise and currents in the Southern Hemisphere to flow counterclockwise.	These affect the path of thermal energy transfer; some areas will get a continuous flow of cool water, while others will get a continuous flow of warm water.
   continents	These cause currents to turn back on themselves.	These cause circular currents in some areas, which affect the path of thermal energy transfer.
   specific heat capacity	n/a	Water can absorb and release large amounts of thermal energy without affecting its own temperature and so can assist in moving thermal energy from one area to another.
   heat of vaporization	n/a	When water melts or evaporates during the hydrologic cycle, it absorbs large amount of thermal energy that can then be released when it changes back to a liquid or solid.

   
   
2. How does living near a large body of water potentially affect the climate you live in?
   
   
   Check your work.
   

   Living near a large body of water will mean there is less variation in temperature than there would otherwise be. This is because the water will release thermal energy when it is cold out and absorb thermal energy when it is warm out, keeping the temperature form reaching extremes.
   
   Depending on if you live near a warm or cool body of water, you could see a warmer climate or a cooler climate than you would otherwise see.