1. Introduction to Antarctica and the Antarctic,
Why is it so cold?

2. Antarctica or Antarctic?
Antarctica is the 5th largest continent on earth and larger than the US and Mexico combined. The word, “Antarctica”, refers to the continent itself. “Antarctic” refers to the entire southern polar region, including the ocean that surrounds this continent.
Antarctica is a continent, the Antarctic is a region.

3. The ice that forms the Antarctic glaciers is accumulated snow fall from hundreds of thousands of years. The continent receives only about 2 inches of snow a year so you can imagine how long it has taken to build up 2 km or more in some places.
Most of Antarctica is covered with over 2 km of snow and ice. These large glaciers move toward the coast under their enormous weight and the force of gravity. When a portion floats out over the ocean these extensions are called ice shelves. The Ross Ice Shelf is as large as Texas.
Source of diagram unknown.but thank you!

4. Ross Ice Shelf
Ice shelves are several hundred feet thick. What you see above the water is only about 10% of the entire thickness of the ice. The ice was formed when snow fell several thousands of years ago, in the center of the continent and was pushed towards the coast under the weight of the glacier and the force of gravity.
This is the edge of a glacier that is floating on the water, but is connected to the remainder that is on the land.
Picture courtesy of: usap.gov

5. When pieces of these shelves break off they are called ice bergs.
The ice shelf from the ocean. What you see is only 10% of the height of this mass of ice. 90% is under the water. This is fresh water and was made from snow fall.

6. The amount of ice in Antarctica plays a very influential role in the Earth’s temperature. Ice reflects most of the sunlight back into the atmosphere without absorbing it. This helps keep the Earth cool.
92% of Antarctica looks like this. Ice streams form where glaciers are moving towards the coast under their enormous weight and the force of gravity.

7. Map courtesy of Australian Antarctic Data Centre
This map shows the continent of Antarctica. The glaciers are white and the ice shelves are in gray. Red dots indicate a science research station.
Antarctica is completely surrounded by ocean. The Southern Ocean is very cold, and is comprised of the largest current on Earth. It flows around the continent from west to east (in a clockwise motion). There is mixing with the ocean waters north, but it is limited. That is one reason Antarctica stays so cold all the time.
Map courtesy of Australian Antarctic Data Centre

8. Here is one definition:
So much for Antarctica but what about the Antarctic? It is best defined by ocean boundaries, although politicians usually define it by latitude for convenience.
Here is one definition:
Any place whose latitude is greater than 66.5o S. In this case here is a map of the Antarctic, defined by what is called the Antarctic Circle. It would include most of the continent of Antarctica and be defined as all places that receive at least one 24 hours of daylight period and one 24 hours of darkness once a year. This boundary would never change as it is defined by latitude.
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9. Another definition, and the one used by scientists, would be everything south of the Antarctic Polar Front. The polar front or, Antarctic Convergence, is where the cold Southern Ocean, which encircles Antarctica, meets the warmer northern water. This is what the Antarctic defined in that way would look like. This boundary changes slightly seasonally and over the years.
This definition includes a much larger area of the Earth and the boundary can change. It is marked by a drop in temperature both in the water and in the air when you cross it.
http//:www. maps.grida.no

10. You have two definitions of what “Antarctic” means and what area of the Earth would be included. Are there any other ways to define this region? How would you draw the map?
One answer: the Antarctic Treaty defines the Antarctic as that portion of the globe south of 60S. Have your students discuss what they think is the best way to define the Antarctic. All these definitions are valid. There are varied definitions that apply to defining the Artic region as well.

11. Why are the Polar regions colder than the rest of the Earth?

12. Consider the black line the total amount of sunlight energy received by the Earth
The black line indicates the amount of sun hitting the earth

13. In this picture the sun’s rays are at a 90o angle at the equator and a 0o angle at the poles. The equator will be receiving lots of sun shine and be very warm while close to the poles will receive very little energy and be much cooler.
Translate what you just learned to the energy coming from the sun to our Earth’s surface. Where is the angle of the sun 90o and where is the angle very low or no sun at all?
Source of diagram unknown

14. This graph represents a one day and one night cycle which is what the South pole experiences each year. Ask your students how this explains why the South Pole is so cold. When the sun is up for 6 months it is still cold, why is that so?
At the South Pole the sun goes below the horizon on the spring solstice (March 21/22) and does not reappear until the fall solstice (Sept 21/22) The same happens at the North Pole only reversed.
Six months of darkness is another reason the Polar regions are so cold.

15. Are the poles equally cold?
You have seen how the orientation of the earth has made for unequal heating of the Earth’s surface. Because of the angle of the sunlight at the Poles they receive less energy and are therefore much colder than the rest of the Earth. You have also seen that the daytime-nighttime cycle provides long periods of darkness for the polar regions which also promote a colder climate
Are the poles equally cold?

16. Areas close to large bodies of water are always more moderate in their climate. This has to do with the ability of water to absorb and retain large amounts of heat. The South Pole is a long way from the ocean and therefore much colder than the North Pole. Did you know the South Pole is not the coldest place in Antarctica. A place called Vostok, a Russian research station, is colder because it is the furthest place from the ocean on the continent of Antarctica.
The Arctic is a large body of water surrounded by land, but the Antarctic is a large land mass surrounded by water. This is one reason the Antarctic is colder than the Artic.

17. As you can see the water flows through the arctic area mixing warm with the cold. In the Antarctic area there are no land masses to restrict the circular flow of the water around the continent so there is little mixing with warmer northern waters.
These maps show the ocean currents for both polar regions. Compare the patterns of the currents. The cold Antarctic water moves in a circular path around the continent and since there are no land masses to deflect it north there is little mixing with those warmer waters. This is quite different from the Arctic and is another reason the Antarctic is colder than the Arctic

18. It’s called adiabatic cooling (or lapse rate)
It’s called adiabatic cooling (or lapse rate). As one ascends in altitude, the air gets thinner, so there are fewer molecules to be holding heat, and colliding with one another to generate it.
Remember this slide? Another reason that the Antarctic is colder than the Arctic, is that the average altitude of Antarctica is almost 2 kilometers. All other things being equal, the Earth’s atmosphere decreases by 6.5oC for every 1000 m of altitude that you ascend ( or about 3.5oF per 1000 ft).
Source of diagram unknown.but thank you!

19. The cold air descends and spreads across the surrounding sea…
Cold air descending from the higher altitudes and blowing over the continent towards the coast is another reason why Antarctica is colder than the Arctic.
The arrows in this map are called vectors. They show the direction the wind is blowing and the strength of the wind. The longer the vector (arrow) the stronger the wind. As you can see the arrows get longer near the coast line. Here the winds become very strong and since they have blown over the land covered with ice they are very cold.
From Parrish & Cassano 2001, J Climatology

20. Sea ice in August In winter, the outward spreading cold winds
help to freeze the
ocean surface, and
the “ice area” of
Antarctica (land plus
sea ice) doubles. In
spring all this ice
reflects sunlight,
keeping the ocean
colder for longer.
The sea ice almost doubles the size of Antarctica in the winter. During this time the Adelie Penguins are living in the pack ice far from the land.
Sea ice in August

21. Sea ice in February During the summer, without the coldest
winds and the
Incessant sun, the
sea ice melts around
most of the continent,
but only for a month
before the ocean
starts to freeze again
as the sun dips lower
and lower.
The sea ice extent during the Antarctic summer, when most of it has melted. During this time Adelie penguins spend part of their time on land in their breeding colonies.
Sea ice in February

22. To sum things up:
Antarctica is a continent almost completely covered with ice and snow and is influential in keeping our planet cool by reflecting the sun’s energy back into space.
The Antarctic is a region and has more than one definition.
Both Polar regions are colder than the rest of the Earth due to the reduced angle of the sun providing less energy, and long periods of darkness when no sun energy arrives.
Antarctica is a colder place than the Arctic because it is a land mass and surrounded by a very cold ocean that does not mix with warmer waters in the north.
Antarctica is also colder because it is so high in altitude.

23. Other Powerpoint presentations for you classroom:
Introduction to the Polar regions, Why is Antarctica so cold?
Introduction to Adelie Penguins, Adelie Penguins march into the classroom.
Penguin Adaptations, This is a harsh continent
Adelie Penguin Behavior, Good manners are always in style
Penguin Predation and Competition, Life is tough for an Adelie Penguin
Adelie Penguins Cope with Global Climate Change
Did You Know, How researchers know what they know
Penguin Quandaries, Can you answer these mysteries
Fun pictures about Adelie Penguin
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