0:00:06.835,0:00:07.905
On our planet,

0:00:07.905,0:00:09.608
we have two polar regions:

0:00:09.608,0:00:11.370
the Arctic, whose name comes from

0:00:11.370,0:00:13.488
the Greek Arktikos, of the North,

0:00:13.488,0:00:14.804
and the Antarctic

0:00:14.804,0:00:16.160
from Antarktikos,

0:00:16.160,0:00:17.726
opposite of the North.

0:00:17.726,0:00:19.978
But there's an easier way to remember them

0:00:19.978,0:00:22.082
if you just remember what surrounds them.

0:00:22.082,0:00:25.749
The Arctic, situated in the Northern hemisphere of our planet,

0:00:25.749,0:00:29.003
is an ocean entirely surrounded by land.

0:00:29.003,0:00:30.547
On the other side of the world,

0:00:30.547,0:00:32.215
the Antarctic is a continent

0:00:32.215,0:00:34.755
entirely surrounded by ocean.

0:00:34.755,0:00:37.730
So, the Arctic has polar bears but no penguins,

0:00:37.730,0:00:40.713
and the Antarctic has penguins but no polar bears.

0:00:41.357,0:00:43.551
Let's talk about the Arctic first.

0:00:43.551,0:00:47.016
The Arctic region consists of a vast, ice-covered ocean

0:00:47.016,0:00:49.627
surrounded by treeless permafrost.

0:00:49.627,0:00:51.194
The area can be defined

0:00:51.194,0:00:53.129
as the region between the Arctic Circle

0:00:53.129,0:00:54.586
and the North Pole.

0:00:54.586,0:00:56.215
If you were to stand at the North Pole,

0:00:56.215,0:00:58.836
everywhere you looked, in all directions,

0:00:58.836,0:00:59.960
would be south.

0:00:59.960,0:01:01.323
But standing at the North Pole

0:01:01.323,0:01:03.255
is difficult to do for very long

0:01:03.255,0:01:05.400
because it's in the middle of an ocean,

0:01:05.400,0:01:08.420
covered by constantly shifting, frozen sea ice.

0:01:08.420,0:01:11.169
If you were to fall into the water at the North Pole,

0:01:11.169,0:01:15.634
you'd fall into water that's 13,980 feet deep.

0:01:15.634,0:01:18.174
Above the water, average winter temperatures

0:01:18.174,0:01:21.593
can be as low as -40 degrees Celsius,

0:01:21.593,0:01:23.349
and the coldest recorded temperature

0:01:23.349,0:01:27.930
is approximately -68 degrees Celsius.

0:01:27.930,0:01:29.263
Despite these incredibly harsh conditions,

0:01:29.263,0:01:31.575
humans have populated areas in the Arctic

0:01:31.575,0:01:33.804
for thousands of years.

0:01:33.804,0:01:37.483
Life in the Arctic includes organisms living in the ice,

0:01:37.483,0:01:39.456
zooplankton and phytoplankton,

0:01:39.456,0:01:41.041
fish and marine mammals,

0:01:41.041,0:01:41.730
birds,

0:01:41.730,0:01:42.367
land animals,

0:01:42.367,0:01:42.985
plants,

0:01:42.985,0:01:45.084
and human societies.

0:01:45.084,0:01:47.183
Okay, what about Antarctica?

0:01:47.183,0:01:50.224
Antarctica is Earth's southernmost continent,

0:01:50.224,0:01:52.885
and it contains the geographic South Pole.

0:01:52.885,0:01:55.588
It's the fifth largest continent on the planet

0:01:55.588,0:01:57.836
at nearly twice the size of Australia.

0:01:57.836,0:02:01.335
Almost 98% of Anarctica is covered by ice

0:02:01.335,0:02:03.778
at least one mile in thickness.

0:02:03.778,0:02:06.859
Conditions in Antarctica are some of the most extreme

0:02:06.859,0:02:08.305
in the entire world.

0:02:08.305,0:02:10.157
On average, it's the coldest,

0:02:10.157,0:02:10.974
windiest,

0:02:10.974,0:02:12.352
driest continent

0:02:12.352,0:02:14.183
and has the highest average elevation

0:02:14.183,0:02:15.725
of all the continents.

0:02:15.725,0:02:18.689
You might think that it snows all the time at the Poles,

0:02:18.689,0:02:20.526
but Antarctica is so dry,

0:02:20.526,0:02:21.996
it's considered a desert

0:02:21.996,0:02:23.111
with annual precipitation

0:02:23.111,0:02:26.252
of only 200 millimeters along the coast

0:02:26.252,0:02:27.614
and far less inland.

0:02:27.614,0:02:29.164
The temperature in Antarctica

0:02:29.164,0:02:32.564
has reached -89 degrees Celsius.

0:02:32.564,0:02:34.995
Because it's so harsh and hard to get to,

0:02:34.995,0:02:37.969
there are no permanent human residents on Antarctica,

0:02:37.969,0:02:40.498
but anywhere from 1,000 to 5,000 people

0:02:40.498,0:02:41.752
reside throughout the year

0:02:41.752,0:02:44.916
at the research stations scattered across the continent.

0:02:44.916,0:02:48.297
Even the most extreme animals fight for survival,

0:02:48.297,0:02:51.100
and only cold-adapted organisms survive there,

0:02:51.100,0:02:53.092
including many types of algae,

0:02:53.092,0:02:54.242
animals,

0:02:54.242,0:02:55.331
bacteria,

0:02:55.331,0:02:56.288
fungi,

0:02:56.288,0:02:57.114
plants,

0:02:57.114,0:02:58.080
and protista.

0:02:59.510,0:03:02.850
But why is Antarctica colder than its northern cousin?

0:03:02.850,0:03:04.468
Well, first, much of the continent

0:03:04.468,0:03:07.075
is more than three kilometers above sea level,

0:03:07.075,0:03:09.431
and temperature decreases with elevation.

0:03:09.431,0:03:12.058
That's why mountaintops have snow on them.

0:03:12.058,0:03:13.853
Second, remember that the Arctic

0:03:13.853,0:03:16.306
is really a frozen ocean.

0:03:16.306,0:03:17.847
The water in the ocean beneath it

0:03:17.847,0:03:20.819
is warmer than the frozen ground in the Antarctic,

0:03:20.819,0:03:23.657
and that warmth is transferred through the ice pack.

0:03:23.657,0:03:26.069
This prevents temperatures in the Arctic regions

0:03:26.069,0:03:27.489
from reaching the extremes

0:03:27.489,0:03:30.686
typical of the land surface of Antarctica.

0:03:30.686,0:03:34.573
Third, the seasons are conspiring against the Antarctic.

0:03:34.573,0:03:36.616
During the aphelion in July,

0:03:36.616,0:03:38.736
when the Earth is the farthest away from the Sun,

0:03:38.736,0:03:41.546
it also happens to be winter in the Antarctic,

0:03:41.546,0:03:43.454
which creates a double-whammy of cold

0:03:43.454,0:03:44.751
for the southern pole.

0:03:44.751,0:03:46.906
But despite being inhospitable,

0:03:46.906,0:03:49.327
the North and South Pole are a big reason

0:03:49.327,0:03:51.431
why our planet is the way it is.

0:03:51.431,0:03:52.940
Both of our polar regions

0:03:52.940,0:03:55.158
are very important climate controllers.

0:03:55.158,0:03:56.886
They help moderate the temperature

0:03:56.886,0:03:58.654
in our temperate zones

0:03:58.654,0:04:00.347
and give us stable weather.

0:04:00.347,0:04:02.475
As sea ice in the Arctic declines

0:04:02.475,0:04:04.558
due to climate change and global warming,

0:04:04.558,0:04:05.908
weather around the globe

0:04:05.908,0:04:08.234
becomes increasing more unstable.