What's it like in Antarctica? - page 1
It's cold, but you guessed that already, it's also the highest and windiest continent. What are the details, how cold is it really and why is it like that?
Where is Antarctica? How big is Antarctica?
Antarctica is the fifth largest of the seven continents. The total surface area is about 14.2 million sq km (5.5 million sq mls) in summer, approximately twice the size of Australia, half as big again as the USA and fifty times the size of the UK.
It is situated over the South Pole almost entirely south of latitude 66°30' south (the Antarctic Circle). It is a very rough circular shape with the long arm of the Antarctic Peninsula stretching towards South America. There are two large indentations, the Ross and Weddell seas and their ice shelves.
The nearest other land masses are South America 1000 km (600 mls) away across the roughest stretch of water in the world - the Drake passage, Australia is 2500 km (1550 mls) away, and South Africa 4000 km (2500 mls) away.
In the winter Antarctica doubles in size due to the sea ice that forms around the coasts. The true boundary of Antarctica is not the coastline of the continent itself or the outlying islands, but the Antarctic Convergence.
Why is Antarctica so cold?
Antarctica in midsummer, the heat
and light available
from the sun is spread over a larger area the closer
you get to the poles, compared to the equator where
the same amount of energy comes down almost
vertically and so is less dispersed.
This means that at the poles the available sunlight and heat is spread over a greater area. The tilt of the earth as the seasons go by make this effect even greater in the winter.
2/ Temperature falls as altitude increases at the rate of about 1C per 100m. Antarctica is also the highest continent with an average elevation above sea level of 2,300m / 7,546 ft or 1.4 miles.
3/ Antarctica is a large landmass and so apart from at the coasts is not affected by sea temperatures which stop it getting quite so cold for so long as in the Arctic.
Antarctica is so cold because it is at the pole, is very high and is a large landmass.
Why is Antarctica considered to be a desert?
A Desert is defined as a region that has less than 254 mm (10 in) of annual rainfall or precipitation.
Antarctica is classified as a desert by this definition. In the interior of the continent the average annual precipitation (in *equivalent of water) is only about 50 mm (about 2 in), less than the Sahara. Along the coast, this increases, but is still only about 200 mm (8 in) equivalent of water. Heavy snowfalls occur when cyclonic storms pick up moisture from the surrounding seas and then deposit it as snow along the coasts.
Unlike other deserts, there is little evaporation from Antarctica, so the relatively little snow that does fall, doesn't go away again. Instead it builds up over hundreds and thousands of years into enormously thick ice sheets.
*this precipitation doesn't fall as water of course, but as snow, the "water equivalent" is the amount of water you would get if the snowfall were collected and melted.
Note - a "dessert" (2 s's) is what you have after your main course, a "desert" (1 s) is the low-rain place.
What is the climate like? How cold does it get in Antarctica?
Antarctica is the coldest, and also the windiest continent.
The lowest temperature ever recorded anywhere on earth, -89.2° C (-128.6° F) was on July 21st 1983 at the Russian Vostok base at the Southern Geomagnetic Pole. It is close to the Pole of Inaccessibility, the point on the Antarctic continent that is the furthest from any other and so the most difficult or inaccessible place to get to. Consistently one of if not the coldest place on earth. This is far from any coast and so is the least affected by the warming effect of the oceans.
The continent is also buffeted by strong winds, calm periods are rare and typically last just a few hours or less. A wind speed of 320 km/h (200 mph) was recorded at the French Dumont d'Urville base in July 1972. The winds flow downwards from the interior toward the coast driven largely by gravity as air cools and becomes denser over the pole.
These winds are known as "katabatic winds", when they reach the coast, they produce west-flowing ocean current known as the East Wind Drift as a result of the rotation of the earth, which has an influence far beyond the immediate coastline.
There are three climatic regions in Antarctica.
The interior of the continent - extremely cold with little snowfall.
The coastal areas - milder temperatures (though still very cold) and much higher precipitation rates.
The Antarctic Peninsula region - which has a warmer and wetter climate, with above-freezing temperatures common in the summer months.
Whiteout in Antarctica
I recall a story of a day where the base doctor had gone out to visit a penguin rookery about two miles away. On the way back the weather had deteriorated and he found himself in a white-out. He thought he saw the base cook, going downhill rapidly on a sledge and waving to him from around 200-300 yards. A few footsteps later, he trod on what he had really seen - a penguin feather stuck in the snow about 10 yards away and blowing in the breeze! Disorienting is definitely the right word!
What is the Antarctic landscape like?
Antarctica consists of two main areas. East Antarctica (Greater Antarctica), and smaller West Antarctica (Lesser Antarctica).
West Antarctica also has the Antarctic Peninsula, it is an extension of the Andes mountains stretching across the ocean from South America. It is thought that if the ice sheet were removed, West Antarctica would actually be a collection of islands.
More than 98 percent of Antarctica is covered with ice, this contains about 70 percent of the world's fresh water. The thick ice cover makes it the highest of all continents, with an average elevation of about 2300 m (about 7500 ft). The highest point on the continent is Vinson Massif 4897 m (about 16 066 feet) and the lowest point yet found is the Bentley Subglacial Trench (2499 m/8200 ft below sea level) in West Antarctica. This trench is covered with more than 3000 m (9840 ft) of ice and snow. Lower points may exist under the ice, but they have not yet been discovered.
The two areas of Antarctica are separated by the Transantarctic Mountains. A range of mountains that stretches across the entire continent, large portions of them being buried under the ice cover. If you stood on the great Antarctic ice sheet all you would see would be ice and snow (and your friend taking a photograph of you standing on the great Antarctic ice sheet - unless it was a selfie).
The Transantarctic Mountains, in places these appear as "nunataks", isolated mountain peaks that show above the surrounding ice with most of the mountains buried. At 3,500 km (2175 miles) long, they are one of the Earth's longest mountain ranges.
It would be far from a continuous smooth sheet though, as it is continuously moving. Glaciers, huge rivers of ice drain the interior of the continent and form ice shelves at the coasts. Where a glacier is moving, the ice cracks and breaks as it is broken by the underlying rock it moves over, and also by different streams meeting that are moving at different speeds. The ice sheet is therefore very dangerous in places as it is broken up by great crevasse fields with some cracks hundreds of feet deep and frequently covered by weak bridges formed of blown snow.
In places, you may see a "Nunatak" an outcrop of rock where one of the taller parts of the Transantarctic mountains peek up through the ice sheet. These nunataks somewhat amazingly can be home to birds such as snow petrels that may build their nests here. This is despite the fact that they are simply isolated unproductive pieces of rock surrounded by miles and miles of cold sterile ice field. Nunataks are very useful to geologists as they give a sample of what the rock is like in that area, where most of it is covered by hundreds or thousands of meters of ice.
Large tabular icebergs are formed at the coasts as the edges of the ice shelves and glaciers calve off into the sea. An ice shelf is formed where a large glacier or even several glaciers begin to float when they meet the sea. The largest of these formations, the Ross Ice Shelf, is the size of the American state of Texas. Ice shelves produce the largest icebergs (called tabular as they are table-like, flat, on top) as the ice is gently fed onto the surface of the sea before eventually breaking off and becoming free floating.
There are at least two active volcanoes in Antarctica, Mount Erebus (3,794 m/12,448 ft) is the highest and has a permanent molten lava lake. The other is on Deception Island, situated just north of the Antarctic Peninsula, a popular stop-off for tourist ships where it is possible to have a warm bath in the volcanically warmed waters while being surrounded by Antarctic ice and penguins.
It is thought that there may be some areas of volcanism under the ice sheet. In some places glaciers and ice streams are flowing very quickly, possibly caused by them being lubricated from underneath by flowing water formed by volcanic activity melting the ice.
What kinds of plants and animals are there in Antarctica?
Antarctica has no trees or bushes at all, vegetation is limited to about 350 species of mostly lichens, mosses, and algae. There are lush beds of such vegetation in some parts of the Antarctic Peninsula. Lichens have been discovered growing on isolated mountains within 475 km (295 mls) of the South Pole. In some places bare rocks are colonised by vibrant red, orange and yellow growths of lichens. Where rock is uncovered by ice for large parts of the summer, green lichens that grow to a few centimeters high can give the impression from a distance of a field of dark grass (albeit a bit tatty). Three species of flowering plants are also found on the Antarctic Peninsula.
Photos JB Thiebot
An endolith, the green band is algae growing inside this
cracked open rock
In some places in the Antarctic continent such as in the dry valleys, rather than growing on rocks, some algae actually grow in the rock. Conditions are so harsh, particularly from strong, drying winds and from blown sand and dust, that it is easier to live in the porous rock despite low light levels, than it is exposed at the surface.
There are no land based vertebrate animals in Antarctica. All the vertebrates there are dependent on the sea for feeding or are migratory and leave the continent when the winter arrives.
The largest truly Antarctic land animals therefore are invertebrates only a few of millimeters in size. These animals, mites, ticks and nematode worms tolerate the low temperatures in the winter by becoming frozen in ice under rocks and stones. They have antifreeze in their bodies and stop all motion and bodily functions while frozen, becoming active again when the ice finally warms up sufficiently to melt. These animals live largely in the Antarctic Peninsula.
The oceans surrounding the continent on the other hand are teeming with great quantities of life. Large numbers of whales feed on the rich marine life, especially krill. Six species of seals and 12 species of birds live and breed in the Antarctic. Crabeater seals are the second most numerous large mammal on the planet after humans and the population of krill has been estimated as outweighing the human population.
The most famous inhabitant of Antarctica has to be the penguin. A flightless bird, but excellent swimmer, penguins live on pack ice and in the oceans around Antarctica. They breed on the land or ice surfaces along the coast and on islands. Best known and most typical are the Adelie and emperor penguins.
Picture credits, copyright pictures used with permission: Earth at Antarctic midsummer equinox diagram - Przemyslaw "Blueshade" Idzkiewicz Creative Commons Attribution ShareAlike 2.0 Generic License / Endolith - picture: Guillaume Dargaud, published under CC3 Attribution Share Alike licence / Emperor penguins - Jerome Maison. © 2005 Bonne Pioche Productions / Alliance De Production Cinematographique. From the Warner Brothers film The March of the Penguins and are used here by permission of Warner Brothers.