The Science Of Desertification 2: The Evolution Of Antarctica

The idea most people have about Antarctica is a continent, very cold, desolate, and thickly icy. Many are not aware that it qualifies in the standard definition of a desert as it receives just about 150mm of rainfall each year. Its very low precipitation implies that although it may be wet due to thick glaciers and surrounding lakes, it has very dry air. In this second article on the science of desertification, we will look into the magnificence of this beautiful continent, how it came to be, and how it metamorphosed into its current state. Also, some information on exciting phenomena and the biodiversity of the region will be included. To keep the article brief, the lengthy discussion of the impact of global warming on the continent will be avoided. The main objective of this article is simply to describe how Antarctica progressed from a tropical biome to a cold and glaciated desert.  

Antarctica is the fifth-largest continent and the latest to be discovered (it was discovered in the 19th century). It is located in the remote Antarctic region which is south of Earth (towards and at the geographic south pole). This region comprises not only Antarctica but everything within the Antarctic plate. This plate is the approximate boundary that separates the region from the other plates (African, South American, pacific, Australian, etc.). The Antarctic region is Antarctica as well as the Kerguelen plateau, archipelagos, islands or territories, ice shelves, seas, and the great Antarctic Ocean (also known as the Southern Ocean). As a continent, Antarctica spans an area of 14.2 million km² and is divided into east and west Antarctica by the transarctic mountains, about 3400km long and one of the largest mountain ranges on earth. In Antarctica are found some important geophysical poles; the south geographical pole, the south geomagnetic pole, and the magnetic south. Western Antarctica has a peninsula that has a milder climatic condition compared to the mainland and where humidity may be higher permitting occasional rainfall. In mainland Antarctica, there are lakes, rivers, and high mountains. The lakes are largely buried underground in ice sheets but do not freeze due to the insulating properties of the overlaying ice. These ice sheets cover the coastal areas as well as large portions of the famous Ross Sea and Weddell Seas. About 80% of the earth's freshwater is frozen in the Antarctic ice. Even some of the highest points and ranges in the continent are buried in the ice and thereby invisible from view.

Political map of Antarctica. Note the peninsula, ice shelves and other minor territories. The closest continent to it is South America at Chile. Chile gives the shortest route to the Antarctica.

Antarctica has not always been a cold desert. It once had a tropical climate teeming with life. There were forests comprising of nonflowering plants. The fossils of many animals have also been found there. It was ice-free for most of its existence and was not even at its current position. About 500 million years ago, Antarctica as part of Gondwana was around the earth's equator having a warm climate. Fossils of organisms that existed at that time have been discovered in present-day Antarctica. It drifted towards the south during the Carboniferous period. After the breakup of Gondwana (which was the southern part of Pangaea) during the Jurassic era, the Antarctic plate began forming to give its current position. Today it is a dry, windy, harshly cold, icy, and barren continent. How did it come to be?

Pangaea, the supercontinent that existed from the Paleozoic era to the early Mesozoic era

From studies of plate tectonics, there is evidence that all the current continents were once together to give the supercontinent called “Pangaea”. This was during the Permian period (299-252 million years ago). Around this time, many plants and animals had developed, shelled organisms and trilobites existed, reptiles had emerged and amphibians were abundant. They all roamed about Pangaea until the great Paleozoic extinction event where most of them were lost. Pangaea began to fissure in the early Jurassic period about 200 million years forming Laurasia and Gondwanaland. About 80 million years ago, Australia and Antarctica had separated from the rest and had begun migrating south until the edge of Antarctica reached the south pole. In the late phase of this breakup, (after the cretaceous period), Australia split from Antarctica and moved northwards while the latter which has always been the southernmost region of Pangaea remained, became isolated, and established on the south pole. The glaciation of Antarctica started after the Permian period and has continued to date. This positioning of Antarctica at the south pole made it very susceptible to freezing as solar radiation could be absent for very periods during the year. Coupled with evidence of gradual reduction of atmospheric carbon dioxide, the development of a new circumpolar current around the antarctic plate which separated the southern ocean from the others, and the numerous cycles of cold winters, it was transformed into a thick cold desert. By the time the earth was 25 million years old, the entire Antarctica was covered in ice.

Climate and temperature

Antarctica has  an extremely cold temperature leading to the formation of giant glaciers. The presence of cold polar regions means the Earth is currently in the ice age.

Antarctica is the coldest place on earth and has an inland temperature of about -30°C during summer and as low as below -80°C during winter although the temperatures may be much lower around the coastal areas. This is because of the thin moisture content of the inland air. The lowest temperature ever recorded on earth according to the geographical records is a chilling 89°C at Vostok station. Antarctica also has the largest icebergs and several active volcanoes.

Other Interesting Features Of Antarctica

Midnight sun and polar night

In both polar circles of the earth, there is a beautiful phenomenon where the sun remains visible at midnight. This effect is due to the axial tilt and rotation of the earth. The earth is tilted at an angle of 23°. During the winter solstice which begins 22 December, the south pole is oriented in the direction of the sun all day. Rotation about the central axis of the earth still preserves the pointing of the south pole towards the sun. This makes the region bright 24 hours long for about 6 months after which it will return to the autumn equinox by 23 September. At the same time, the north pole experiences the opposite effect; the polar night where darkness can persist 24 hrs long at some point. During this event, the sun is never seen as the sun never rises above the horizon. This phenomenon reverses on the 21 June summer solstice, where the midnight sun is in the north and polar night in the south. 

The sun does not set at certain times in summer. Therefore it remains bright even at midnight.

Southern lights

Many are familiar with the northern lights (Aurora borealis) which occur in the Arctic region. A similar phenomenon also occurs in Antarctica and is called Aurora australis. It is not so common as not many people can witness it. If intense enough, it can be seen in Australia, New Zealand, and the southernmost regions of South America but this is very rarely seen there.

Who lives there? 

During the summer solstice, thousands of tourist visit the continent. However, there is a limit on the number of people who can visit at a particular time.

99% of the landmass of Antarctica is covered with ice due to extremely low temperatures. It is in fact, the largest ice sheet in the world and can have a thickness of 2km. The coasts, peninsula, and islands within the Antarctic Circle are more capable of hosting life due to milder climatic conditions and this is reflected in the more abundant flora and fauna present compared to the mainland. As such, no one lives there permanently. Most of those who live there are scientists (comprising marine biologists, geophysicists, climatologists, geologists, etc.) from several countries around the world who stay temporarily performing research and experiments in camps and stations, others are simply tourists and travelers. As many as 5000 people may be there in summer but the numbers drop to about a thousand when the winter comes. Winter conditions can be harsh, dark, and cold. It's extremely difficult to access the continent during the winter which is why most people leave before the season arrives. The winter can last for about 5 months. However, there are few permanent bases set up for scientific research. 

Wildlife and biodiversity

Penguins are the national animals of Antarctica. They are the only animals that breed in the continent's interior. They have adaptations to survive the terrible cold. Several species are found in the archipelagos and the peninsula.

Not many animals can be found in Antarctica today. Fully terrestrial mammals are never found and the only land-dwelling vertebrates are penguins and seals. Most living organisms are found around the coastal areas, sub-antarctic islands, and the peninsula where the climate is less extreme and liquid water exists. Emperor penguins are the only animals that breed in the interior of Antarctica. There are no penguins at the North Pole/Arctic Circle. Likewise, there are no polar bears in Antarctica ( you can only find them in the Arctic). there are several species of penguins in Antarctica, some of which are found exclusively there.

Most life in Antarctica are microbes which are present in hundreds of species. The most common land animals are some species of nematodes. Whales, seals, fishes, and some crustaceans are also found in the southern oceans. Conditions are better suited for life in the oceans compared to the mainland. All these animals have adaptations to help survive the extreme cold. The only animal found in both north and south poles are the orcas commonly known as killer whales, which migrate to and fro, from the north to the south poles. Only two insect species have ever been found and reptiles do not exist there. Plants are rarely found in the interior but where they exist, they are usually lichens, algae, or mosses.

Will Antarctica change in the future?

Due to the dynamics of geophysical processes, there is a chance that Antarctica could return to its former state. With the rising effects of global warming, the increase in heat may lead to ecological changes which can lead to transformation of the biome and possibly extinction of species.