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HT1.1 5.1a,b

5.1a

  • The global hydrological cycle’s operation as a closed system (processes, stores and flows) driven by solar energy and gravitational potential energy.

What is a system? What is the difference between an open and closed system?

A system is a collection of interconnected components that work together to achieve a common purpose. In environmental science, an open system allows for the transfer of both energy and matter between the system and its surroundings, while a closed system exchanges only energy, keeping matter within its defined boundaries.

How does energy cause flows to happen within the system?

Energy causes flows in a system by transferring from one form to another, such as from potential energy to kinetic energy, which can result in movement or work being done. This transfer can occur through various processes, including heat flow, mechanical work, and electromagnetic interactions.

This can drive processes such as evaporation, where heat energy from the sun causes water to transition from a liquid to a gaseous state, entering the atmosphere and affecting local weather patterns.

5.1b

  • The relative importance and size (percentage contribution) of the water stores (oceans, atmosphere, biosphere, cryosphere, groundwater and surface water) and annual fluxes between atmosphere, ocean and land.

Key words

  • Stores - Various reservoirs where elements like carbon or water are held. In the hydrological cycle, stores refer specifically to water stores.

  • Fluxes/flows - The movement of elements like carbon or water in various cycles which are essential for maintaining balance within the ecosystem. In the hydrological cycle, fluxes/flows refers specifically to the flow of water.

  • Residence time - The average time a particular molecule of water will remain in a specific body of water. It is calculated by dividing the volume of the water by the inflow or outflow rate, indicating how long it takes for water to cycle through that system.

What are the sizes of these stores and fluxes?

Stores

Diagram showing the distribution of global water stores

  • Oceans - 96.9%

    • Largest store

    • 3,600 year residence time

  • Icecaps/cryosphere - 1.9%

    • Mostly freshwater

    • 15,000 years depending on size

  • Groundwater - 1.1%

    • Up to 10,000 years for deep groundwater; 100-200 years for shallow groundwater.

  • Rivers and lakes/surface water - 0.01%

  • Soil - 0.01%

  • Atmosphere - 0.0001%

Fluxes/flows

Diagram showing the Hydrosphere and Hydrological Cycle

In 10,000km²/year

  • Land to atmosphere - 73

  • Atmosphere to ocean - 373

  • Land to ocean - 40

  • Ocean to atmosphere - 413

  • Atmosphere to land - 113