School › Polar regions › Ages 10–11
The Arctic and Antarctica compared
Two ends of the Earth, two very different places. Compare the Arctic and Antarctica, discover why the polar regions are deserts, watch sea ice grow and shrink, and test whether huddling really keeps penguins warm.
Read
The Arctic Circle lies at about 66.5° north and the Antarctic Circle at 66.5° south. Inside them, the Sun stays up for at least one whole day in summer and does not rise for at least one day in winter. At the North Pole the Sun sets around 21 September and does not rise again until around 21 March.[4][3]
The poles are cold mainly because sunlight reaches them at a low, slanting angle. Snow and sea ice are white and reflect far more sunlight back to space than dark ocean water does.[2][7]
The Arctic is an ocean mostly surrounded by land. Antarctica is a continent surrounded by ocean, covered by an ice sheet up to 4.8 km thick that holds about 90% of the world's fresh water found at the surface. The lowest temperature ever recorded on Earth, −89 °C, was measured at Vostok station in Antarctica.[1][5]
The polar regions are deserts! Antarctica's snowfall is equal to only about 150 mm of rain a year, and some Arctic areas get about as little as the Sahara.[5][3]
Sea ice is frozen seawater. When it freezes it pushes out most of its salt. Around Antarctica the sea ice grows from about 2.8 million km² in late summer to about 18.6 million km² in winter; in the Arctic it changes from about 6.3 to 15.5 million km² (long-term averages).[7][1]
Life depends on the ice. Algae growing under sea ice feed krill, which penguins eat. Polar bears hunt seals at breathing holes in the ice; under their fur, whose hairs are clear and shiny, their skin is black. Emperor penguins huddle together at −43 °C, about 21 birds per square metre, slowly shuffling so that birds take turns in the warm middle.[9][8][10]
Try it: Does huddling keep you warm? A fair test
You need
- Seven identical small plastic bottles or cups (about 200 ml)
- Warm tap water (an adult checks it is not hot)
- A measuring jug
- Two thermometers
- Rubber band or string
- A tray and a cool place (a fridge, a cold windowsill or outside in winter)
- Timer
Safety
Use warm tap water only; an adult checks the temperature first. Use plastic, not glass. Wipe up spills straight away.
What to do
- Fill all seven bottles with the same amount of warm tap water from the same jug.
- Measure and write down the starting temperature.
- Stand six bottles in a tight ring around the seventh and hold them together with a rubber band: this is the huddle. Put a thermometer in the middle bottle.
- Stand one more bottle on its own, a hand's width away from the huddle, with the second thermometer. (If you only have seven bottles, take one from the ring and use a smaller ring of five.)
- Leave everything in the same cool place for 20 minutes.
- Read both thermometers. Which bottle lost less heat?
What happens, and why?
A bottle on its own loses heat from all of its sides to the cold air. In the huddle, the middle bottle is surrounded by other warm bottles, so it loses heat more slowly. Emperor penguins pack tightly together in their huddles to keep warm, and the huddle slowly moves so birds on the cold outside get a turn in the middle.[10]
Play: Arctic, Antarctic or both?
Sort each fact: is it true for the Arctic, for Antarctica, or for both?
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Quiz
Other ages: Ages 6–7 · Ages 15–16