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.
3. 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
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. 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.
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.
8. 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.
http//:www.en.wikipedia.org
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.
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?
11. Why are the Polar regions colder
than the rest of the Earth?
22. Each of these sun’s
rays are equal in size
and therefore amount
of energy, but notice
at 45o
angle the
amount of land
covered by the ray is
larger than when the
angle is at 90o
.
23. 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
24. In this diagram you see the angle of the sun is marked for the various
places on the Earth. The Earth is in this position with respect to the sun on
the equinoxes.
Source of diagram unknown
25. The Earth is tilted with respect to the sun and this is how the angles of the
sun translate as the Earth rotates around it. These angles change with the
season. Notice that the sun is at a 90o
angle at latitude 23.5o
N. This is the
Tropic of Cancer and no place north of this line will ever see the sun at 90o
.
Source of diagram unknown
26. The angles of the sun’s rays rotate from the extremes of these two
diagrams. Notice at the North and South Poles the angle of the sun never
gets greater that 23.5o
above the horizon. The latitudes where the sun’s
angle is 0 at mid-winter are called the Arctic and Antarctic Circle,
respectively (66.5 N & S). The low angle of the sun in the polar
regions is one reason why these places are so cold.
Position of the Earth on
the Equinoxes
Position of the Earth on
the Solstices
Source of diagram unknown
27. SIN 80 = 0.98 or 98%
SIN 70 = 0.94 or 94%
SIN 60 = 0.87 or 87%
SIN 50 = 0.77 or 77%
SIN 40 = 0.64 or 64%
SIN 30 = 0.50 or 50%
SIN 20 = 0.34 or 34%
SIN 10 = 0.17 or 17%
SIN 0 = 0.00 or 0%
Translate: If the angle of the sun is 80o
then that region receives
98% of the energy it would if the sun were 90o
. Or places on the
Earth where the sun is 60o
above the horizon receive 87% of the
energy that a place where the sun is straight up or 90o
receives.
As the angle of the sun gets smaller towards the poles the amount of
energy received by the earth is not a linear relationship. It is a function
of the angle as you see in the chart below
28. Insolation is the amount of sun energy hitting the earth
at a given place.
The total amount of energy hitting each of these latitudes in a year is
represented by the number of boxes under the curve. Notice the
amount hitting the poles is much smaller than the rest of the earth. This
is another reason why the poles are so cold.
Source of diagram unknown
29. Before you go the next slide predict how this graph will change if you go north,
say to Iceland where the latitude is 64.1o
N, very near the Arctic Circle.
Day / Night Cycle Graph
midnight
noon
noon
30. Did you guess right? Because Reykjavik is near the Arctic Circle there are
periods of almost 24 hours sunlight and periods of almost darkness all
night. Now let’s go to a place above the Circle say Thule, Greenland.
Before you go to the next slide predict what the graph will look like.
31. Did you predict correctly? Since Thule is above the Arctic Circle there are
days of 24 hours sunlight and nights of 24 hours of dark. How would this
graph change if we went to a similar latitude in the South? Predict first
then go the next slide.
32. How did you do? Believe it or not this is almost the exact same graph as the
one for Thule only the seasons are reversed because McMurdo is in the
Southern Hemisphere. Two more: Predict what this graph looks like at the
Equator and at the South Pole.
33.
34. 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.
35. 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?
36. Average Winter o
F Average Summer o
F
South Pole -76 -18.5
North Pole -15 35
Notice that the South Pole average summer temperature is colder than the
average winter temperature at the North Pole
Come up with some ideas why this is so.
Compare the average T at the North and South Poles
37. 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.
38. http://www.whoi.edu/
http://www.aad.gov.au
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
39. 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 6.5o
C for every 1000 m of altitude that you ascend
( or about 3.5o
F per 1000 ft). Source of diagram
unknown.but thank you!
40. The cold air descends and spreads across the surrounding sea…
From Parrish & Cassano 2001, J Climatology
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.
41. Sea ice in
August
www.noaa.gov
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.
42. Sea ice in
February
www.noaa.gov
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.
43. 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.
44. 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
Go to www.penguinscience.com The education page.
Editor's Notes
Antarctica is a continent, the Antarctic is a region.
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.
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.
When pieces of these shelves break off they are called ice bergs.
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.
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.
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.
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.
If the earth were flat like this the amount of sun hitting each part of the earth would be the same
The black line indicates the amount of sun hitting the earth
The amount of sun rays or energy would be less
The amount of energy would be less even though the size of the Earth has not changes. This means less energy per sq mile so the Earth would be colder.
The Earth surface would not get any energy from the sun and would be a very cold place indeed.
Ask your students which of these places under the sun is the hottest. More energy per unit of area will be the hottest so the area under the 90o ray will be hotter.
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.
If you would like your students to do some math, have them subtract the angle of the sun shown here from 90 and you will get the latitude of each of these lines which are marked on the left hand side. These lines are very important lines on our globe. They are from top to bottom, the Arctic Circle, the Tropic of Cancer, The Equator, the Tropic of Capricorn and the Antarctic Circle. The Earth is only in this position with respect to the sun two days a year, the equinoxes in March and Sept. On these days everywhere on the earth receives 12 hours of day light and 12 hours of darkness.
Again some math. Here is the extreme of the Earths sun angles and happens on the solstices (June and Dec). See if your students can figure out a relationship between the angle of the sun and the latitudes in this diagram.
Have your students compare these two diagrams. A good classroom activity which illustrates this yearly cycle is for students to mark the suns shadow somewhere around the school building every third or fourth day at the same place and time each day, for a full school year. North facing walls work well. In addition they should make a special note of the shadow length on the equinoxes (Sept and March) and the winter solstice (Dec) Use a strip of adding machine tape to mark the shadow. The tape can be rolled out each time and taped to the building then rolled up and put away. At the end of the year have the students graph the date (x axis) against the shadow length (y axis).
Skip this slide if your students are not familiar with trigonometry
The units here are Watts per square meter. Watts is a unit of energy, square meter the area of land. The units are not important only that the amount of energy changes with latitude. Have your students calculate the number of boxes under each of theses curves. That would equal the total amount of energy reaching each of these places in one year. Then have them graph the latitude ( x-axis) against amount of energy (y axis) and they will see the total amount of energy received by the poles is very small compared to the equator and the other latitudes.
Look at this diagram and note that it shows the daytime nighttime cycle for Columbus Ohio. You can see the days are longer in June than in December, however every day gets some sunlight and therefore some warming energy. Have your students make the predictions for the shape of the next few graphs by drawing them in their journal or on a white board. Discuss with the class some ideas before going to the next slide.
If the students are struggling with this help them by asking the question. The further north you go will the days be longer in the summer or shorter?
Thule is well above the Artic circle so there are many days of 24 hour sunlight and 24 hour darkness. Have your student predict what a city ON the artic circle would look like.
This is almost the exact same graph as the Thule one. You can print this out, cut it down the line at about June 21 and then turn the pages around. Ask your students why the cut would be made at June 21st?.
If your students get this correct they have a good understanding of this exercise..
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?
Some students might need to be reminded that when the temperature is in the negative degrees, the larger the number, the colder it is. Based on this data, the South Pole is much colder thatn the North Pole.
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.
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.
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.
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.
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.
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.
