Heat Transfer
Heat transfer occurs in both the hydrosphere and the atmosphere to disperse solar energy around the globe. This reduces the temperature difference in Earth, cooling tropic climates and warming polar climates to temperatures that would not be expected if there was no heat distribution.
Heat Sinks
A heat sink is a reservoir that absorbs and stores thermal energy. The hydrosphere and atmosphere are heat sinks, particularly the hydrosphere because water can absorb much more thermal energy than air. When the air is warmer than the ocean surface, the ocean absorbs energy from the air, and when the air is cooler than the ocean surface, the ocean releases energy into the air. This phenomenon is the reason why large bodies of water affect the climate of its surrounding areas.
Types of Heat Transfer that Occurs in the Atmosphere & Hydrosphere
- convection - thermal energy transferred by the movement of heated matter
- conduction - thermal energy is transferred through matter as particles come into contact with each other
- radiation - thermal energy is transferred just through space, not requiring a medium
Processes of Heat Transfer in the Atmosphere
In the atmosphere, convection currents are the primary process that transfers heat. Convection currents are circular current created by the movement of warm and cold air. The process happens in steps:
near the equator, solar radiation hits the earth at the highest levels.
near the equator, solar radiation hits the earth at the highest levels.
- solar radiation affects the air around the equator, which heats up rapidly and becomes less dense
- colder, more dense air from above displaces the warm, less dense air into the atmosphere
- warm air then spreads out towards the poles and cools
- the now-cooled air sinks back down and creates a high pressured area
- high pressured cool air pushes more low density warm air into the atmosphere, and the cycle repeats indefinitely
Effects of Heat Transfer on the Atmosphere
Heat transfer in the atmosphere is what creates air currents . Air usually flows from areas of high pressure to low pressure, which is what causes air current (commonly known as wind). Because of the permanent bands of high/low pressure, there are air currents called prevailing winds that flow nearly always. Due to the rotation of Earth, prevailing winds curve around Earth instead of going straight north to south and vice versa. These air currents can affect and influence ocean currents (e.g. Gulf Stream)
Processes of Heat Transfer in the Hydrosphere
The water cycle is fuelled by heat transfers between and in both the atmosphere and the hydrosphere, further spreading heat between the atmosphere and the hydrosphere. Another method of heat transfer that occurs in the hydrosphere is called thermohaline circulation in the ocean. In the ocean, thermohaline circulation is the primary process responsible for energy transfer, which includes all ocean currents caused by changes in temperature and salinity. The circulations, like convection currents, occurs in steps:
- water travelling towards the poles gets colder
- the water becomes more concentrated with salt as surface water evaporates and sea ice forms (sea ice rejects salt during formation)
- cooling and increased salt concentration causes water at the poles to be more dense, sinking towards the ocean floor
- warm water from the equator replaces the cooled water; the cycle then repeats
Effect of Heat Trasfer on the Hydrosphere
Heat transfer in the hydrosphere is cause of water currents. This movement of water that this heat transfer causes affects other Earth systems as well, like the formation of sea ice that contributes to the cryosphere, or land formations that make up the lithosphere.