WATER or  H2
"Of all the conditions important to terrestrial life, liquid water is the most important. Not only is it a solvent in which organic chemicals can be transported and can react with one another, it is a vital ingredient in photosynthesis, the process which converts sunlight into sugars and thus provides the energy source for the majority of life."

It is also very good at dissolving inorganic elements and minerals, like NaCl or salt.  Salt is a generic term and living things use a lot of different salts.  Life evolved in the oceans which were a hot stew of chemicals mostly salts call the "primordial soup".  Today all living things carry "the sea" inside in the form of blood that is salty AKA saline. 

Water also holds heat and releases it slowly, moderating night and day temperatures.  Evaporation of water is cooling.  The fact that the Earth is 71% covered in water makes most places on Earth moderated by big bodies of water. Contrast this with the extremes of temperature on Mars,  + 1° F to -178° F.  Water vapor, along with CO2 and other greenhouse gases, is a protective envelope of atmosphere that moderates day/night temperatures. 

Gases, as well as ions, dissolve in water.  Dissolved oxygen and carbon dioxide make life in water possible since fish and other water animals breathe oxygen and extract dissolved oxygen from the water. 
Water plants like algae take  dissolved carbon dioxide out of the water and make glucose during photosynthesis. 90% of the biomass of Earth is in the oceans. 


Very good slide show of various aspects of water cycle.  Click HERE

  WHERE DOES WATER COME FROM?    Most of Earth's water is locked up in rock. 
As the plates dive down at subduction zones water is injected into the magma which thins the magma as it moves up into volcanoes.  When volcanoes vent various gases this and the water in the melted rock is ejected as water vapor. 
"Earth's approximate water volume (the total water supply of the world) is 1,360,000,000 km3 (326,000,000 mi3)." 

Where is water located?
- Most water is located in the oceans
- there is only one ocean
- it covers more than 70% of the Earth's surface
- it contains 97% of all the surface water on Earth
- the water is SALTY 
- 90% of the biomass of Earth is in the oceans

- 35 gm of dissolved salts in each kilogram of sea water
- salt increase the boiling point and decrease the melting point of water
- the salts remain in the liquid when sea water evaporates or freezes so the vapor or ice is more or less fresh water

- 3% of water is FRESH
- 2% is frozen into polar ice caps, snow, and glaciers
- less than 1% is in rivers, groundwater, and lakes
-- a smidgen  0.001% is in the atmosphere as water vapor, clouds, and fog.

- fresh water mostly has bicarbonate ion (HCO3-) which is also the basis of the buffer system in our bodies
- a buffer resists a change in pH, so it keeps the pH stable 



The ocean has three temperature layers.

1.  The top layer goes down to 250 m, temperature varies according to latitude and season from near freezing 0oC at the poles to near 30oC near the equator.

2.  The middle layer is between the top and bottom, is called the thermocline and the temperature decreases with depth.

3.  The deep layer is below 1000 m, the temperature is near 0oC - 5oC  and there is no seasonal change.


" Surface currents, shown at right, are driven by the winds. Warm water is red and cold water is blue. The Trade Winds propel ocean water westward along the equator, and when it strikes a continent, it is diverted poleward. However, a narrow return flow also occurs along the equator. In mid-latitudes the currents are driven eastward by the Westerlies. The opposing wind belts cause currents in all the ocean basins to form gyres, or giant loops."

- At the surface the winds drive the water which forms large loops
- The Coriolis force results in clockwise loops in the northern hemisphere and counterclockwise loops in the southern hemisphere.

- Local winds and continents also influence the paths of the loops

What is an El Niño?  "El Niño is an oscillation of the ocean - atmosphere system in the tropical Pacific having important consequences for weather around the globe. "

Click HEREto read about the impacts of El Nino on climate and how that effects the economy of countries that are affected. 


"Thermohaline (Deep) Circulation

    * Evaporation makes water more saline and denser
    * Freezing makes water more saline and denser
    * Cold water is denser than warm water

A combination of surface and deep flow creates a giant global heat conveyor. The coldest and densest water forms off Antarctica and flows along the ocean floors until it reaches an obstacle. Then it rises and joins the surface circulation. As water loops around the North Pacific gyre, it becomes extremely warm. Even though the amount of water that passes from the Pacific to the Indian Ocean is not great, the amount of heat it carries is. It cools a bit rounding Africa, then warms in equatorial latitudes and carries  water up the Atlantic into the Arctic. Finally the water cools and sinks, mixes with cold bottom water, and begins the cycle again."

- As surface water cools in polar regions it becomes more dense, sinks and flows toward the equator along the bottom.
- near the equator the water is warmed and rises, finishing the loop.
- water in the deep ocean mainly forms layers that do not mix very much.


The Gulf Stream warms western Europe while the Labrador current cools eastern North America.  Milwaukee is at the same latitude as northern Spain, and Labrador at the same latitude as Ireland and southern England.  Without the Gulf Stream Ireland and England would be as cold as Labrador in winter

THE WATER CYCLE - Evaporative cycles of water
Surface water evaporates from land, lakes, rivers, oceans.  Evaporated water is nearly pure, the ions stay behind

As water evaporates and turns to vapor it rises in the atmosphere, cools and forms clouds.  The hotter the air, the more vapor can be held. 

At some point vapor reaches saturation and then begins to condense (reaches the dew point) around a little dust mote of some kind (called condensation nuclei) and a drop of water forms.  If it is very cold, it will be ice.

It begins to fall and it usually hits rising warmer air and evaporates before hitting the ground. The rest is precipitation as rain, sleet or snow. 

If it doesn't melt and evaporate, it may also be swept up by rising air, and can go up and down several times forming hail and when it is large enough in finally fall all the way to Earth.

- When water falls it either evaporates, trickles down into the soil or it moves overland until it reaches the ocean.  The mid continental divide determines whether the water goes into the Pacific or the Atlantic.



In Wisconsin, there is a mid-mid continental divide at Sunnyslope road (going west on I-94) that determines if the water is going to eventually drain into the Mississippi and into the gulf, or into the Atlantic ocean.  By law, all water removed east of Sunnyslope is supposed to go back into the "watershed" of lake Michigan and all water west into the Mississippi watershed.  This has caused a lot of wrangling between Milwaukee county sewage district and Waukesha county. 

(1 miles = 5280 feet)

So how high are those clouds? 

THE WATER CYCLE -  Biological cycles of water 
For some reason I am not finding good pictures to illustrate the cycle of water thru biological systems. 

All living things need water. 
- First and foremost, all biochemical reactions take place IN a water environment, inside the cell which is basically a "bag of water". 
- Water is a chemical used in making the building blocks of organic material. It is used in making glucose from sunlight and CO2 (photosynthesis). 
- Water is released when the building blocks are strung together a process known as dehydration synthesis. 
- In larger multicelled animals and plants there is a circulation system (blood, sap) based on water that moves nutrients throughout the organism to "feed" the live cells. 
- In plants (picture on the right) water that evaporates from the leaves provides the vacuum that results in water flowing into roots and up into even the high branches of trees like Sequoias along the living cells under the bark. 
- In animals oxygen exchange takes place across water.  Water animals take up dissolved oxygen across their gills which are immersed in the oxygen containing water.  Land animals need a wet water rich mucous in the lungs in which oxygen dissolves and can enter the cells and then into the blood stream for distribution to every cell in the body. 
- Respiration is the breakdown of glucose to produce energy by all living things that results in the production of CO2 and water. 
- In animals water is used to get rid of excess metabolites (urine) and for evaporative cooling (sweating). 
- So water is taken into living things and then released by various mechanism.  There is a water "balance" of intake and output that must be maintained.  Humans that dont get enough water suffer dehydration, blood pressure drops, they get light headed and eventually die if water is not replenished. Plants that dont get enough water suffer dehydration, lose turgidity in the cells, wilt and eventually die if they dont get water. 

ROLE OF ARCTIC ICE IN GLOBAL WARMING - melting glaciers   youtube


Review questions:
Discuss the relative distribution of fresh and salty water on earth.
How does salt effect water?
Discuss the difference in the salt content of ocean vs fresh water.
Discuss the three different temperature layers of the ocean.
Discuss the circulation of the ocean.
How do the surface current effect climate? Give an example.
Discuss the evaporative cycle of water. Draw a picture to illustrate this cycle.
What is required for water in a cloud to condense?
Discuss the biological cycle of water in living things.
How long can humans live without water?  Without food?