Human earth shapers/ETHS101/Earthsystems/Hydrosphere

Hydrosphere

From the darkness of space our planet is blue. This is because it has a hydrosphere and atmosphere. These outer shells surround the geosphere. In this learning pathway, we will find out about these important Earth systems, like the Water Cycle.

Think and Share

LEARNING ACTIVITY REQUIRED - WENOTE DISCUSSION

The water cycle

In the infographic, on the water cycle (above), you can see the main elements of the water cycle, which involves the geosphere, the hydrosphere, and the atmosphere. Although H2O is mainly liquid, it can also be a gas in the atmosphere or a solid (ice) in the atmosphere, mountain tops, or ice caps. The infographic below tells us where the water is stored on Earth and in what form. Note that most of the water is in the liquid state in the world's oceans and seas and is salty. Freshwater is only 3% of all the Earth's water, and most of that is in the form of ice.

Which water reservoir holds its water the longest?

Earths water reservoir

• Select one from the below
  • The atmosphere
    • Incorrect. Consider using the table to your right OR think a little "lower".
  • The ocean
    • Incorrect. Consider using the table to your right.
  • Groundwater
    • Correct. Well done, read below for more information.
  • Lakes
    • Incorrect. Consider using the table to your right.
  • They all hold water for the same amount of time.
    • Incorrect. There is a better answer available to you, try again.

If you thought the answer was Ground Water you were correct. In some areas of the Great Artesian Basin that spreads west of Australia's Great Dividing Range into the dry inland, groundwater extracted can be millions of years old.

Does more water evaporate from the ocean, or from the land?

Water transfer between reservoirs in the water cycle

• Select one from the below
  • The Ocean
    • Correct. Well done, there is a significant difference between the two, which leads us to the question below.
  • The Land
    • Incorrect. Consider using the table to your right.

If more water is evaporating from the ocean than precipitating into the ocean, how come we are worried about sea level rise?

• Ocean precipitation = 398,000 km3/year
• Ocean evaporation = 434,000 km3/year

Although more water evaporates from the ocean, river runoff from the continents into the ocean make up the balance.

Water - Unique characteristics that make water what it is.

Unusual Properties of Water

High boiling point	High melting point	High specific heat
High heat conductivity	High heat of evaporation	High heat of freezing
Maximum density at 4°C (pure water)	High surface tension	High viscosity
High dielectric constant

How do these unique properties of water affect global temperatures?

• The oceans can hold a lot of energy without changing temperature – thermal inertia
• Important vehicle for heat and energy transfer between the oceans and atmosphere
• Transfers energy from the equator to the poles
• Thawing and freezing of ice at the poles moderates global temperatures, absorbing and releasing energy without changing ocean temperatures

What about ocean circulation? How does that affect weather and climate?

• Ocean circulation can be divided into surface and deep currents
• The surface currents are driven by the winds, by the rotation of the earth, and by differences in seawater density, which cause differences in the height of the sea surface
• Deep ocean circulation, also known as the thermohaline (thermo = temperature, haline = salt) circulation, is driven by density differences, caused by differences in temperature and salinity
• Both deep ocean and surface ocean circulation move heat, gases, and nutrients around the planet, and play a key role in climate and weather
• Learn more by watching this short video on the deep ocean circulation and its role in climate

Summary

Now that you know some interesting things about the hydrosphere have a look at the next page on the atmosphere.