Human earth shapers/ETHS101/Earthsystems/HydrosphereMCQ

=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.

In the infographic, on the water cycle (below), 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 water cycle
The infographic indicating where is Earth's water 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.



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

Share your thoughts on the WeNote pannel below. We encourage you to share your thought, however, if you are stuck you can find the answer to this question at the bottom of this learning page.


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

Water - Unique characteristics that make water what it is.
In this section, we consider the unique properties of water, and how these affect global temperature, weather and climate.

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.

WeNote Activity: If more water is evaporating from the ocean than precipitating into the ocean, how come we are worried about sea level rise?
 * Answer: Although more water evaporates from the ocean, river runoff from the continents into the ocean make up the balance.