Antarctica – The Ice Kingdom

Antarctica is the southern continent of the earth, on which the South Pole itself is located. It is located in the middle of the Antarctic, with which it is often identified in everyday speech. Other names are the southern continent and the Antarctic continent. Antarctica has an area of ​​about 14 million square kilometers and is almost completely covered by the Antarctic ice sheet. Geographically, a distinction is made between the regions West Antarctica and East Antarctica.

The existence of an undiscovered southern continent has been suspected since ancient times and was called Terra Australis (“southern land”). With the exploration of the South Pacific, New Zealand and Australia by Abel Tasman in the 17th century and James Cook in the 18th century, its possible location was limited to the high southern latitudes. However, the pack ice of the Southern Ocean and the extreme weather conditions made it impossible to explore this region for a long time. It was not until the end of the 19th century that discoveries made it clear that the interior of the southern polar region, for which the name Antarctica was coined, actually contained land of continental dimensions.

Antarctica ice sheet

The most noticeable feature of the Antarctic continent is that it is almost completely frozen. The Antarctic ice sheet is the largest ice mass on earth. Around 90% of the earth’s ice and 70% of the world’s freshwater reserves are contained in the ice sheet, which is up to 4500 m thick. A comparable large area of ​​ice on the earth is currently only found in Greenland.

When the ice sheet of Antarctica formed a few million years ago, the continent sank due to the enormous weight of the ice masses in the earth’s crust. When the ice melts, the land is expected to rise again. If the sea level had melted completely, it would rise by around 61 meters at the same time.

“Land” under and over the sea

Photo by Cassie Matias on Unsplash

This topographic map of Antarctica without ice takes into account the isostatic land elevation as well as the rise in sea level caused by the ice melt. It gives an idea of ​​what Antarctica looked like 35 million years ago, before the great ice sheets formed.

Antarctica’s freshwater ice makes up most of the land surface and is therefore counted as part of the continent. Large parts of Antarctica lie below sea level, but are covered in ice to above sea level and are generally considered part of the continent.

Without the ice cover, the contours of the continent would look completely different from what is normally shown. West Antarctica would be divided into three large parts: the Antarctic Peninsula, Marie Byrd Land, and the Vinson Massif. East Antarctica would consist of a land mass with huge bays (e.g. Aurora Subglacial Basin and Wilkes Subglacial Basin) and fjords (e.g. at what is now Amery Glacier or under the South Pole). The East Antarctic land mass was dotted with many lakes and inland seas, the bottom of which sometimes extends well below sea level.

Lakes under the ice

In Antarctica, there are lakes with liquid water under the ice called subglacial lakes. These consist mainly of fresh water. Radar image (RADARSAT-1) of Lake Vostok from space. The ice over the lake has a smooth surface. To date, more than 150 subglacial lakes have been found. The largest of these is Lake Vostok, which was discovered in 1996 through satellite imagery near the Russian Vostok station. It is about 250 km long, 50 km wide, has a water depth of up to 1200 m and lies at a depth of 3700 to 4100 m under the ice. The fact that the lake has not frozen despite its average temperature of -3 ° C is due to the high pressure of around 30 to 40 megapascals under the ice cover, as the melting point of the ice falls at high pressure. In addition, Antarctica has surface lakes (with surfaces that are partially frozen year-round) such as Lake Fryxell, and hypersaline lakes such as Lake Don Juan, which is considered to be the saltyest body of water on earth with a salinity of over 40%.

Rivers

Another geographical peculiarity of the Antarctic is the extensive lack of superficial rivers. The largest river in Antarctica, the Onyx, is a 30 km long meltwater river that only flows in the late Antarctic summer (February, March). In 2006, however, it was established that the subglacial lakes are believed to be connected by a network of subglacial rivers and that pressure equalization and water transport take place between them. The subglacial rivers are partly above and partly below sea level. The red-colored blood cases discovered in 1911 consist of iron-containing hypersaline water that comes from a subglacial lake.

Antarctic oases

Large (largely) ice-free regions in Antarctica are known as Antarctic oases. The largest oases in Antarctica are the dry valleys in Victoria Land. Antarctic oases are rocky and often contain freshwater lakes. In these areas, the Antarctic flora and fauna can be explored. They are also important for finding fossils.

Glacier in Antarctica

The Antarctic ice sheets are constantly moving towards the shores of the Southern Ocean. There are areas in which the ice moves significantly faster than in adjacent areas. These are known as ice rivers. They are a special form of the glacier. The ice streams can be hundreds of kilometers long, 50 kilometers wide and 2 kilometers high, and their speeds can be up to 1000 meters per year. Shear forces occur at the edges of the ice streams, which deform the ice and make it softer. Numerous crevasses form there. Most of Antarctica’s ice rivers are called glaciers, but not every glacier is an ice river. Where ice streams flow into the sea, glacier tongues (“ice tongues”) can protrude far into the sea.

Flora and fauna

While the Southern Ocean and the huge pack-ice zone that surrounds Antarctica, as well as the offshore islands are full of life, the interior of the continent is barren and empty, as hardly any more highly developed forms of life are found here. Instead, these areas are predominantly populated by microorganisms, mosses and lichens, as well as some invertebrates. But these ecosystems are unique on earth. On the one hand, the environmental conditions are very extreme, and on the other hand, the region is – due to the former – still largely free of human influences.

An unusual and at the same time very simple ecosystem is found in the dry valleys near the McMurdo station, which is predominantly populated by microorganisms, mosses and lichens and some invertebrates. Due to the few organisms that occur, the connections and mutual relationships as well as their adaptation to extreme living conditions can be examined very comprehensively.

Surprisingly, it was found that life is not only limited to the few ice-free regions, but can also be detected in unexpected places. In the dry valleys, for example, algae and lichens have been found that live within sandstone rocks. Even in the vastness of the Antarctic ice sheet, various algae and other organisms were found in smaller ice crevices and meltwater lakes on the glaciers.

Leave a Reply

Your email address will not be published.