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Water and Carbon Cycles

Global water stores, their size and residence times

  • 2 things to know
  • Component 2

Overview

Where the planet's water actually sits — oceans, ice, groundwater, soil, atmosphere — with the share held in each and how long a molecule stays there, from days in the air to millennia in an ice sheet.

What you need to know

Answer each one before you reveal it.

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Key term

Roughly how much water is there on Earth in total?

Numbers

What percentage of the world's water is held in the oceans?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Roughly how much water is there on Earth in total?

    Model answer

    Earth holds roughly 1.386 billion cubic kilometres of water in total. The figure has changed very little over geological time.

  2. 2

    What percentage of the world's water is held in the oceans?

    Model answer

    The oceans hold about 96.5 per cent of all water on Earth. Salinity makes almost all of that store unusable for drinking or irrigation.

  3. 3

    What proportion of Earth's water is fresh?

    Model answer

    Fresh water makes up about 2.5 per cent of all water on Earth. Most of that fresh water is locked in ice or held deep underground.

  4. 4

    Which store holds most of the world's fresh water?

    Model answer

    Ice sheets, ice caps and glaciers hold roughly two thirds of Earth's fresh water. Antarctica alone accounts for the great majority of that ice.

  5. 5

    Roughly what share of global water sits in the cryosphere?

    Model answer

    The cryosphere holds about 1.7 per cent of all water on Earth. Antarctic and Greenland ice dominate the total.

  6. 6

    How large is the groundwater store compared with surface fresh water?

    Model answer

    Groundwater holds around 1.7 per cent of all water, which is far more than every lake and river combined. Rivers and lakes together hold well under a hundredth of that amount.

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