Antarctic Answers

by Deb on September 10, 2011

Antarctica

In some ways Antarctica is a completely different world, one we can’t live in without lots of help. If you want to do the quiz close your eyes and click, otherwise read on for the answers.

1.     Penguins have several ways of keeping warm which all work together so they can survive the coldest place on earth.

  • They have a thick layer of blubber (fat) under their skin to insulate them.
  • They can control the blood flow to their feet and decrease it when they are cold. This isn’t on purpose – we do it too. This is why your feet and hands go white when it is cold.
  • They have a heat exchanger in their legs. Rather than large arteries going down to their feet as we have, they split into many small capillaries that run closely together with veins coming back from the feet. The heat from the arteries warms the returning blood and only cool blood goes down into the feet so not much heat is lost.
  • They don’t have muscles in their flippers. The muscles are in the main body mass and the flippers are controlled by long tendons. This means less blood is needed out in the flippers where it can get cold. It also makes them more streamlined for faster swimming.
  • They have specially modified feathers. They are denser than other birds, with around twenty feathers per square centimetre. The feathers have a large downy section on the base and the rest of the feather is short, shiny and overlaps to make a cover. The downy section traps air that is warmed by body heat and insulates the penguins, the same way down quilts work. The tiny barbs on the feathers hook together like three dimensional velcro, meaning that the feathers don’t move or slide over each other easily. When penguins are in the water the pressure pushes the feathers flat and they lose much of their air layer, but when they get out the feathers spring back up into position. This lets the air pockets form and warm up quickly.
  • Like most waterbirds they oil their feathers to make them waterproof.
  • Emperor penguins huddle together throughout the winter. They shuffle along and gradually take turns being inside and out as the whole mass slowly moves along. Have a look at the video at the bottom to hear David Attenborough describe it.

Image courtesy of Liam Quinn

2.     The Antarctic Polar vortex is an enormous cyclone that forms in the upper troposphere and stratosphere around the pole during winter. This means it is not at the surface but higher. The fact that there is a continent in the south but the Arctic is open ocean surrounded by land has created very different weather and atmospheric conditions. It gets much colder in Antarctica and the polar vortex is stronger and lasts for longer.

It concentrates chemicals that have been produced around the world and found their way into the stratosphere. During the winter in high, extremely cold clouds, some of these chemicals react and form chlorine that is then trapped and builds up. When the sun returns the chlorine reacts with and destroys ozone, causing the Antarctic ozone hole. Luckily, most of the dangerous chemicals have been banned and there are less and less in the atmosphere so the hole is healing.

3.     Ice cores are drilled out of Antarctica and the Greenland ice sheet and tell us a lot about ancient climates. Ice forms from seasonal snow so is in layers that can be used like tree rings. Thicker layers indicate more snow, which implies more precipitation and a wetter climate. Especially important is the air bubbles, which provide tiny samples of what the ancient atmosphere was like. This is one of the ways we have seen the growth of industrial pollution and the effects of volcanoes and can make direct measurements of the ratio of gases such as carbon dioxide.

The water the ice is made from also helps us measure temperature. Many elements come in different forms called isotopes. Oxygen has three isotopes, O-16, O-17 and O-18. Oxygen-18 has two extra neutrons in the nucleus, so water made with it will be fractionally heavier than water with oxygen-16. This means there is a measurable difference in how easily they evaporate. When it is warmer there is a higher ratio of O-18/O-16, when it is colder there is a lower ratio.

ice core

Ice core with clearly visible seasonal layers.

4.     There are two advanced plants on Antarctica, Antarctic hair grass and Antarctic pearlwort. There are also several lichens and mosses, but advanced plants are the ones that have different structures like roots, leaves and veins. These two are flowering plants and they are found on the slightly warmer and wetter western peninsula as well as islands such as South Georgia.

Pearlworts are widespread members of the carnation family and are cushion plants, a common form in extremely cold, harsh conditions. The grow very compact stems at the same rate, so no stems are sticking out above the others. Underneath the surface many of them let the leaves die to create insulation. They tend to grow very slowly but have increased longevity, some cushion plants are hundreds and even possibly thousands of years old. They have very deep tap roots to allow them to get moisture and give them stability.

Antarctic_Pearlwort

Image courtesy of Liam Quinn

5.     The photo above is indeed a topographical map produced using radar through the ice sheet. The clue to why it is special is the little circle next to it labelled ‘Chicxulub.’ If you are a palaeontology type geek you might recognise this as the crater from the meteor thought to have killed the dinosaurs, or more technically caused the mass extinction event at the Cretaceous-Tertiary boundary.

As you can see the ridge circled in Antarctica is far larger, and gravity mapping seems to show a large mass of mantle rock pulled up in the middle of it. This indicates an enormous impact, possibly from a meteor almost 50km wide. It is possible to guess at a date from the geology of about 250 million years ago, and there were definitely profound changes in the earth then.

Crater_zoom_with_gravity_overlay a

A combined gravity and topographical image showing the crater.

That is the date of the Permian mass extinction, the great grand daddy of all mass extinctions. Up to 96% of all marine species died out, as well as 70% of the land species. More than half the families of living creatures became extinct, there have been estimates that only a few thousand species survived. The earth afterwards was a very different and much emptier place, leading to the rise of animals we are more familiar with today.

There were also possibly enormous geological changes brought on by the impact. When it occurred all the continents were joined into the mega-continent Pangaea. There were already distinct regions, including the large southern super-continent of Gondwana, which included Antarctica, South America, Australia, India, Africa and Madagascar. Much later Gondwana broke up, and Australia split from Antarctica along a rift going through the impact crater. It’s possible that the enormous impact weakened the crust and created the fault that eventually produced Australia.

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