A word about Earth’s water cycle

View larger. | Earth is unique in our solar system in having liquid water on its surface. Water is essential for life. And it’s a key to Earth’s climate, helping to transport heat around the planet. Yet – despite the global view offered by satellites – Earth’s water cycle is not well understood. ESA’s Climate Change Initiative is looking at a range of climate variables linked to the water cycle. Image via ESA.

Originally published at ESA – The European Space Agency.

Although the amount of water on Earth is fixed, it continually cycles between the oceans, atmosphere and land. Powered by the sun, this circulation and conservation of Earth’s most precious resource is a crucial component of our weather and climate.

Earth’s water cycle is vital to life and climate

Even though the water cycle is one of the most important processes operating on our planet, this fundamental system is still poorly understood. And it is crucial for sustaining life and controlling our weather and climate.

Understanding if, and how, climate change is modifying Earth’s water cycle is increasingly important. Plus, understanding how Earth works shapes environmental policy and decision-making.

The total amount of water present on Earth is fixed and does not change. Powered by the sun, water continually circulates between the oceans, atmosphere and land. This circulation and conservation of Earth’s water, known as the water cycle, is a crucial component of our weather and climate. Image via ESA.

A warmer climate changes the water cycle

A warmer climate leads to changes in evaporation patterns over the land and oceans. Thus, increasing the moisture content of the atmosphere influences weather patterns. This causes concerns, especially for water consumption and agricultural needs.

By consistently mapping soil moisture and ocean salinity, the European Space Agency’s SMOS mission is improving our understanding of the role these two key variables play in regulating the water cycle.

Earth’s water is always in movement. The natural water cycle describes the continuous movement of water on, above and below the surface of the Earth. Water changes states between liquid, vapor and ice. These processes happen in the blink of an eye or over millions of years. Image via USGS.

Changes in evaporation and ocean circulation

Soil moisture refers to the water in the spaces between soil particles. Primarily, soil moisture is a function of the rates of evaporation and precipitation. But the type of soil and vegetation cover influence the rates that water filters through the soil and runoffs from the surface.

In the oceans, variations in the salinity of the surface waters depends on the addition or removal of freshwater through evaporation and precipitation. Also, the variations in polar oceans depend on the freezing and melting of ice. Thus, the salinity and temperature influence the density of seawater. Together, these variations drive ocean circulation patterns and moderate climate. They do so by bringing warm surface waters to higher latitudes and cool deeper waters back to equatorial regions.

Bottom line: Although the amount of water on Earth is fixed, it continually cycles between the oceans, atmosphere and land. Powered by the sun, this circulation and conservation of Earth’s most precious resource is a crucial component of our weather and climate.

Learn more with ESA’s water cycle video.

Source: ESA’s Earth’s Water Cycle

Via ESA

Read more: Was ancient Earth a water world?

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