Formation of the ice sheet of Antarctica. The ice in the west of Antarctica broke up from the inside What are the reasons for the formation of a glacier in Antarctica
This question can only be answered by a person who is thirsty for knowledge, striving to reveal all the secrets of nature, who dared to live and work on a glacier for many days, and often even months. Not so many years, apparently, separate us from that moment, happy for mankind, when the astronauts who set off for the shining disk of the Moon will have the opportunity to “look at their native Earth from the outside”, to see the entire globe of the earth. And our dear will appear before them as a giant blue drop of water hanging in the blackness of space. This is not surprising, because the surface of the Earth is covered by more than 70% of the waters of a single World Ocean, divided by the continents into four large water areas: the Pacific, Atlantic, Indian, Arctic oceans ...
ocean of ice
But there are others on earth ocean, and it consists not just of liquid water, but of solid - ice. And he appears as a white mantle against a blue background. In our time, this mantle is pretty shabby; it was preserved on the body of the Earth only in separate patches, the largest "flap" is the icy continent of Antarctica. But not so long ago, if we keep in mind the age of the Earth as a planet, only 10 - 12 thousand years ago, the mantle of ice descended down to the temperate latitudes of the northern hemisphere, covering most of the land south of the equator. Nearly sea level has risen by 200 meters when most of the ice has melted. Ice - the solid phase of water
Ice - the solid phase of water. The massive transformation of water into ice marks the transition to the last stage of mineral formation. Ice differs most from all low melting point. Therefore, it crystallizes from a melt, which is essentially water, only at low temperatures. Once having arisen, the ice itself creates conditions favorable for its further distribution. Ice is the only mineral on Earth that cannot serve as a substrate for the development of any form of organic life. Ice crystallization requires a temperature below zero, so it appears only where the summer is too short and cool for the snow that has fallen during the winter to melt all over. So far, there are not so many such places on the globe. But it is worth the earth's atmosphere, its lower layers, to cool down quite a bit - by 2-3 ° on average per year, as the water quickly begins to turn into ice, first in the mountainous and polar regions, and then, when the increase in ice spaces leads to a new cooling, ice will spread to more southern latitudes. This process has been repeatedly repeated on earth. A powerful ice sheet covered half of Europe and vast territories in Asia and America, reaching the latitude of Havana. The total volume of continental ice then was three times the volume of all modern glaciers. The role of the ice age in the life of the Earth is enormous. Suffice it to say that it was during the second interglacial era that man learned to make fire.Snow shell of the Earth
If we talk about the shells of the Earth, then it can be noted that a person knows five concentric spheres in which the Earth is enclosed - the lithosphere - the stone sphere, the hydrosphere - water, the biosphere - the sphere of life, the atmosphere - air ... Some believe that an artificial shell has already been created - technosphere, or, as academician Vernadsky called it, "noosphere". This is a moot point. And the question of the existence of the chionosphere is equally controversial - snow shell of the earth.There is nothing alive on the glaciers
There is nothing alive on the glaciers. Only by chance will a beautiful butterfly be blown there from the valley, and it, burned by the cold, will fall on the snow, which will melt slightly under it; many such butterflies killed by ice can be found on the mountain glaciers of Central Asia. Only an air giant, a snow vulture-kumai, will fly over the glaciers, run, fleeing from a snow leopard, a mountain goat - teke, in Antarctica - a clumsy teenage penguin will wander out of curiosity, in the Arctic - a polar bear will cross the ice dome with mighty jumps, heading from one arctic seas to another ... But all these are transiters, hurrying to leave the inhospitable chionosphere as quickly as possible.
Glaciers shape the climate
About 16 million square kilometers, that is, more than one tenth of the Earth's land area, is occupied glaciers. The volume of ice in them is 30 million cubic kilometers. Glaciers are a product of the climate. Like electronic memory machines, they absorb climatic information - all the countless changes in the weather - "remember" them, sum them up and, having "highlighted" the decisive trend, react to it with their behavior. The weather can change in any way - warming follows cold snaps, snowfalls follow rains and fogs ... The predominance of such conditions that contribute to the development of glaciers can be very difficult to notice in an endless string of weather. Only the reaction of the glacier, the change in its size, will show the "general line" of all weather and climate changes.There seems to be nothing more painful than dependence on the weather,- wrote Richard Baird, he was the first to visit both poles of the Earth. To somehow reduce this dependence is the task of geophysicists, including those who study the icy expanses of our planet. After all, ice on the surface of the Earth plays an important role in shaping the modern climate. And glaciers play the role of "climate conductors"... The mankind of the future will cover the white spots of glaciers with a network of research stations; it will learn to use glaciers as helpers in the very difficult task of predicting the climate. For decades, scientific settlements have been continuously existing in the icy Antarctica under the flags of different countries of the world. During the International Geophysical Year, scientists from 26 countries explored glaciers in different parts of the world. One hundred and three permanent stations made observations directly on the glaciers.
Research results
Research results conducted by scientists in Antarctica are truly sensational: the icy continent receives more solar heat in summer than equatorial countries despite the sun being low on the horizon. It turns out that the low altitude of the sun is more than compensated by the round-the-clock supply of sunlight, high air transparency and low cloudiness. More 100 thousand calories of heat per year for every square centimeter in the center of Antarctica, the same amount as in the sunny resort Crimea ... Why is the sun powerless to overcome its cold? Why is Antarctica cold? And the point is that ice itself creates a simple but powerful protection from the sun's rays. This protection is a white snowy surface that reflects almost all the heat that comes to it. Out of 100 thousand calories per square centimeter, only 4-5 thousand remain, and their snow, having warmed up by several degrees, gives up to air, the temperature of which (-50, -70 °) is very far from the temperature of snow melting.The ice of the Arctic and Antarctic is by no means eternal. In our time, in connection with the impending global warming caused by the ecological crisis of thermal and chemical pollution of the atmosphere, the mighty shields of frost-bound water are melting. This threatens a great disaster for a vast territory, which includes low-lying coastal lands of various countries, primarily European ones (for example, Holland).
But since the ice sheet of the poles is capable of disappearing, it means that it once arose in the process of the development of the planet. "White caps" appeared - a very long time ago - within some limited interval of the geological history of the Earth. Glaciers cannot be considered an integral property of our planet as a cosmic body.
Comprehensive (geophysical, climatological, glaciological and geological) studies of the southern continent and many other areas of the planet have convincingly proved that the ice cover of Antarctica arose relatively recently. Similar conclusions were drawn for the Arctic.
First, the data of glaciology (the science of glaciers) indicate a gradual increase in ice cover over the past millennia. For example, the glacier covering the Ross Sea was much smaller just 5,000 years ago than it is now. It is assumed that then it occupied only half of the current territory covered by it. Until now, according to some experts, the slow freezing of this gigantic ice tongue continues.
Drilling wells in the thickness of the continental ice gave unexpected results. The cores clearly showed how the next layers of ice were frozen over during the last 10-15 millennia. Spores of bacteria and plant pollen were found in different layers. Consequently, the ice sheet of the mainland grew and actively developed during the last millennia. This process was influenced by climatic and other factors, since the rate of formation of layers of ice varies.
Some of the bacteria (up to 12 thousand years old) found frozen in the thickness of the Antarctic ice have been revived and studied under a microscope. Along the way, a study of air bubbles walled up in these huge layers of frozen water was organized. Work in this area has not been completed, but it is clear that in the hands of scientists were evidence of the composition of the atmosphere in the distant past.
Geological studies have confirmed that glaciation is a short-term natural phenomenon. The oldest global glaciation discovered by scientists happened over 2000 million years ago. Then these colossal catastrophes were repeated quite often. The Ordovician glaciation falls on an epoch remote from our time by 440 million years. During this climatic cataclysm, a great number of marine invertebrates died. There were no other animals at that time. They appeared much later, to become victims of the next freeze attacks, covering almost all continents.
The last glaciation, apparently, has not yet ended, but retreated for a while. The great retreat of the ice occurred about 10 thousand years ago. Since then, the powerful ice shells that once covered Europe, a significant part of Asia and North America have remained only in Antarctica, on the Arctic islands and above the waters of the Arctic Ocean. Modern humanity lives in the period of the so-called. interglacial period, which will have to be replaced by a new advance of ice. Unless, of course, before they melt completely.
Geologists have received a lot of interesting facts about Antarctica itself. The great white continent, apparently, was once completely free of ice and was distinguished by an even and warm climate. 2 million years ago, dense forests, like taiga, grew on its coasts. In areas open from ice, it is possible to systematically find fossils of a later, Middle Tertiary time - imprints of leaves and twigs of ancient heat-loving plants.
Then, more than 10 million years ago, despite the cooling that began on the continent, the local expanses were occupied by vast groves of laurels, chestnut oaks, laurel cherries, beeches and other subtropical plants. It can be assumed that these groves were inhabited by animals characteristic of that time - mastodons, saber-toothed, hipparions, etc. But much more striking are the oldest finds in Antarctica.
In the central part of Antarctica, for example, the skeleton of a fossil lizard of Lystrosaurus was found - not far from the South Pole, in rock outcrops. A large reptile of two meters in length was distinguished by an extremely terrible appearance. The age of the find is 230 million years.
Lysrosaurs were, like other animal lizards, typical representatives of the heat-loving fauna. They inhabited hot swampy lowlands, abundantly overgrown with vegetation. Scientists have discovered an entire belt in the geological sediments of South Africa, brimming with the bones of these animals, which is called the Zone of Listrosaurs. Something similar has been found on the South American continent, as well as in India. Obviously, in the early Triassic period, 230 million years ago, the climate of Antarctica, Hindustan, South Africa and South America was similar, since the same animals could live there.
Scientists are looking for an answer to the riddle of the birth of glaciers - what global processes, imperceptible in our interglacial era, 10 millennia ago bound a huge part of the land and the oceans under the shell of hardened water? What is causing this dramatic climate change? None of the hypotheses is convincing enough to be generally accepted. Nevertheless, it is worth remembering the most popular ones. Three hypotheses can be distinguished, conditionally called space, planetary-climatic and geophysical. Each of them gives preference to a certain group of factors or one decisive factor that served as the root cause for the cataclysm.
The space hypothesis is based on the data of geological surveys and astrophysical observations. When establishing the age of moraine and other rocks deposited by ancient glaciers, it turned out that climatic catastrophes happened with strict periodicity. The earth froze in the interval of time, as if specially allotted for this. Each great cooling is separated from the others by a period of approximately 200 million years. This means that after every 200 million years of the dominance of a warm climate, a long winter reigned on the planet, powerful ice caps formed. Climatologists turned to the materials accumulated by astrophysicists: what could be the reason for such an incredibly long time between several iterative (regularly occurring) events in the atmosphere and hydrosphere of a space object? Perhaps with space events comparable in scale and time frame?
Calculations of astrophysicists call as such an event - the revolution of the Sun around the galactic nucleus. The dimensions of the Galaxy are extremely large. The diameter of this cosmic disk reaches a size of about 1000 trillion km. The sun is located at a distance of 300 trillion km from the galactic core, so the complete revolution of our star around the center of the system is delayed for such a colossal period of time. Apparently, on its way the Solar system crosses some region in the Galaxy, under the influence of which another glaciation occurs on Earth.
This hypothesis is not accepted in the scientific world, although it seems convincing to many. However, scientists do not have the facts on the basis of which it could be proved or at least convincingly confirmed. There are no facts confirming the galactic influence on the million-year fluctuations in the planet's climate, except for a strange coincidence of numbers. Astrophysics has not found a mysterious region in the Galaxy where the Earth begins to freeze. The type of external influence, due to which something similar can happen, has not been found. Someone suggests a decrease in solar activity. It seems that the “cold zone” reduced the intensity of the solar radiation flux, and as a result, the Earth began to receive less heat. But this is just speculation.
Supporters of the original version came up with a name for the imaginary processes taking place in the star system. A complete revolution of the solar system around the galactic core was called a galactic year, and a short interval during which the Earth is in an unfavorable "cold zone" was called a cosmic winter.
Some proponents of the extraterrestrial origin of glaciers are looking for climate change factors not in the distant galaxy, but inside the solar system. For the first time such an assumption was made in 1920, its author was the Yugoslav scientist M. Milanković. He took into account the tilt of the earth to the plane of the ecliptic and the tilt of the ecliptic proper to the solar axis. According to Milankovitch, the key to the great glaciations should be sought here.
The fact is that depending on these slopes, the amount of radiant energy of the Sun reaching the earth's surface is most directly determined. In particular, different latitudes receive different numbers of rays. The interposition of the axes of the Sun and the Earth, which changes over time, causes fluctuations in the amount of solar radiation in different regions of the planet and, under certain circumstances, leads the fluctuations to the stage of changing the warm and cold phases.
In the 90s. 20th century this hypothesis has been extensively tested using computer models. Numerous external influences on the position of the planet relative to the Sun were taken into account - the Earth's orbit slowly evolved under the influence of the gravitational fields of neighboring planets, the Earth's trajectory was gradually transformed.
The French geophysicist A. Berger compared the obtained figures with geological data, with the results of a radioisotope analysis of marine sediments, showing temperature changes over millions of years. The temperature fluctuations of oceanic waters completely coincided with the dynamics of the process of transformation of the earth's orbit. Consequently, the cosmic factor could well have provoked the beginning of a cooling of the climate and global glaciation.
At present, it cannot be said that the Milankovitch conjecture has been proven. First, it requires additional long-term checks. Secondly, scientists tend to adhere to the opinion that global processes could not be caused by the action of only one factor, especially if it is external. Most likely, there was a synchronization of the action of various natural phenomena, and the decisive role in this sum belonged to the Earth's own elements.
The planetary-climatic hypothesis is based precisely on this provision. The planet is a huge climate machine that, with its rotation, directs the movement of air currents, cyclones and typhoons. The inclined position with respect to the plane of the ecliptic causes non-uniform heating of its surface. In a sense, the planet itself is a powerful climate regulator. And her inner strengths are the reasons for his metamorphosis.
These internal forces include mantle currents, or the so-called. convection currents in layers of molten magmatic matter that composes the mantle layer underlying the earth's crust. The movements of these currents from the core of the planet to the surface give rise to earthquakes and volcanic eruptions, mountain building processes. These same currents cause deep splits in the earth's crust, called rift zones (valleys), or rifts.
Rift valleys are numerous on the ocean floor, where the crust is very thin and easily breaks under the pressure of convection currents. Volcanic activity is extremely high in these zones. Here, mantle matter constantly pours out from the bowels. According to the planetary-climatic hypothesis, it is magma outpourings that play a decisive role in the oscillatory process of the historical transformation of the weather regime.
Rift faults on the ocean floor during periods of greatest activity generate enough heat to cause intense evaporation of seawater. From this, a lot of moisture accumulates in the atmosphere, which then falls to the surface of the Earth as precipitation. In cold latitudes, precipitation falls in the form of snow. But since their precipitation is too intense and the number is large, the snow cover becomes more powerful than is usually the case.
The snow cap melts extremely slowly, for a long time the arrival of precipitation exceeds their consumption - melting. As a result, it begins to grow and transforms into a glacier. The climate on the planet is also gradually changing, as a stable area of non-melting ice is formed. After some time, the glacier begins to expand, because the dynamic system of uneven income-expenditure cannot be in balance, and the ice increases to an incredible size and binds almost the entire planet.
However, the maximum glaciation becomes at the same time the beginning of its degradation. Having reached a critical point, an extremum, the growth of ice stops, having met the stubborn resistance of other natural factors. The dynamics has become reversed, the rise has been replaced by a decline. However, the victory of "summer" over "winter" does not come immediately. Initially, a protracted "spring" begins for several millennia. This is a change of short bouts of glaciation with warm interglacials.
Earth civilization was formed in the era of the so-called. Holocene interglacial. It began about 10,000 years ago, and, according to mathematical models, will end at the end of the 3rd millennium AD, i.e. about 3000. From this moment, another cooling will begin, which will reach its apogee after 8000 of our calendar.
The main argument of the planetary-climatic hypothesis is the fact of periodic change of tectonic activity in rift valleys. Convection currents in the bowels of the Earth excite the earth's crust with different strengths, and this leads to the existence of such epochs. Geologists have materials that convincingly prove that climatic fluctuations are chronologically linked to periods of the greatest tectonic activity of the bowels.
Rock deposits show that the next cooling of the climate is accompanied by significant movements of thick blocks of the earth's crust, which were accompanied by the appearance of new faults and the rapid release of hot magma from both new and old rifts. However, the same argument is used by supporters of other hypotheses to confirm their correctness.
These hypotheses can be considered as varieties of a single geophysical hypothesis, since it relies on data on the geophysics of the planet, namely, it relies entirely on paleogeography and tectonics in its calculations. Tectonics studies the geology and physics of the movement of crustal blocks, while paleogeography studies the consequences of such movement.
As a result of multi-million-year displacements of colossal masses of solid matter on the earth's surface, the outlines of the continents, as well as the relief, changed significantly. The fact that thick strata of marine sediments or bottom silts are found on land directly indicates the movements of crustal blocks, accompanied by its sagging or uplift in this region. For example, the Moscow region is composed in large quantities of limestone, abounding in the remains of sea lilies and corals, as well as clayey rocks containing mother-of-pearl ammonite shells. It follows from this that the territory of Moscow and its environs was at least twice flooded with sea waters - 300 and 180 million years ago.
Each time, as a result of the displacement of huge blocks of the crust, either a lowering or an uplift of a certain section of it occurred. In the case of subsidence, ocean waters invaded the mainland, the seas advanced, and transgression occurred. When the sea rose, they receded (regression), the land surface grew, and often mountain ranges rose in place of the former salt basin.
The ocean is the most powerful regulator and even generator of the Earth's climate due to its colossal heat capacity and other unique physical and chemical properties. This water reservoir controls the most important air currents, air composition, precipitation and temperature patterns over vast areas of land. Naturally, an increase or decrease in its surface area affects the nature of global climatic processes.
Each transgression significantly increased the area of saline waters, while the regression of the seas significantly reduced this area. Accordingly, climate fluctuations occurred. Scientists have found that periodic global cooling roughly coincided in time with periods of regression, while the advance of the seas on land was invariably accompanied by climate warming. It would seem that another mechanism of global glaciation has been found, which, perhaps, is the most important, if not exceptional. However, there is another climate-forming factor accompanying tectonic movements - mountain building.
The advance and retreat of oceanic waters passively accompanied the growth or destruction of mountain ranges. The earth's crust, under the influence of convection currents, wrinkled with chains of the highest peaks here and there. Therefore, an exceptional role in long-term climatic fluctuations should still be given to the process of mountain building (orogeny). Not only the surface area of the ocean depended on it, but also the direction of air currents.
If a mountain range disappeared or a new one arose, then the movement of large air masses changed dramatically. Following this, the long-term weather regime in the area was transformed. So, as a result of mountain building, local climates radically changed throughout the planet, which led to a general rebirth of the Earth's climate. As a result, the emerging trend towards global cooling was only gaining momentum.
The last glaciation is tied to the epoch of the Alpine mountain building, which is ending before our eyes. The Caucasus, the Himalayas, the Pamirs and many other highest mountain systems of the planet became the result of this orogeny. The eruptions of the volcanoes Santorin, Vesuvius, Nameless and others are provoked by this process. We can say that today this hypothesis dominates modern science, although it is not fully proven.
The hypothesis received an unexpected development, moreover, in the application to the climatology of Antarctica. The ice continent acquired its current appearance entirely due to tectonics, only the decisive role was played not by regression and not by a change in air currents (these factors are considered secondary). The main influence factor should be called water cooling. Nature froze Atlantis in exactly the same way that a person cools a nuclear reactor.
The "nuclear" version of the geophysical hypothesis is based on the theory of continental drift and paleontological findings. Modern scientists do not question the existence of the movement of continental plates. Since, due to the convection of the mantle, the blocks of the earth's crust are mobile, this mobility is accompanied by a horizontal displacement of the continents themselves. They slowly, at a rate of 1-2 cm per year, crawl along the molten mantle layer.
The mutual arrangement of the continents changed over time, which affected the climate of the Earth, since air and ocean currents depended on it. The fossilized bones of the Lystrosaurus in Antarctica and the extremely numerous similar finds in Africa, South America and India confirm the assumption of scientists that once all these southern lands, including Australia as well, were united into one supercontinent.
The single southern continent of Gondwana existed for over 200 million years: from 240 to 35 million years ago. About 35 million years ago, tectonic movements of the crust finally split it into the current "pieces", one of which turned out to be Antarctica. The split had a negative effect on her climate, as she became isolated.
Previously, the Antarctic shores were washed only by two cold currents, the action of which was fully compensated by warm ocean currents coming from Australia docked with Antarctica. After all the pieces of the supercontinent spread in different directions and left Antarctica alone in the middle of the ocean, it began to be actively washed by many currents, which eventually formed a continuous stream - the so-called. circumpolar flow.
It surrounded Antarctica and gained strength as the "fifth ocean" - the southern waters of the Antarctic region - grew and deepened. Every second, the current carries more water than all the rivers of the planet, which is not surprising, given the average depth of the "southern ocean", equal to 3 km. The current covers all layers of water to the very bottom, being the greatest climatic barrier in nature. This fantastic barrier absorbs all the heat that is only supplied to the white mainland from the outside.
It turned out to be sufficient to lower the air temperature in the Antarctic region by only 3 ° C for the barrier to start acting like a refrigerator. Now the growth of snow and ice cover was inevitable even if the relatively warm regime on the continent persisted. The glacier gradually, in the process of growth, displaced heat to the outskirts, where it was absorbed by the circumpolar current.
An ice sheet in the west of Antarctica has cracked from the inside, which may explain why large icebergs are constantly breaking off from it and why it is collapsing so quickly, according to an article published in the journal Geophysical Research Letters.
Fracture caused by the splitting of the Western Ice Sheet
Antarctica at its foot
©NASA/Nathan Kurtz
“Today, no one doubts that the Western Antarctic Ice Sheet will melt, the question is when this will happen. The formation of such cracks and faults causes the glacier to retreat at a record high rate, and adds to the chances that the current generation of people will witness the complete collapse of this ice sheet, ” - said Ian Howat (Ian Howat) from Ohio State University (USA).
Howat and his colleagues came to this conclusion by analyzing satellite images taken during one of the recent disasters in Antarctica - a giant iceberg with an area of 582 square kilometers broke away from the Western Ice Sheet in late July 2015.
Photographs of the surface taken by the Sentinel probes and thermal maps of the glacier collected by the Landsat 8 probe led scientists to suspect that some deep processes at the very foot of the ice mass were to blame for the formation of this giant iceberg.
To test this theory, climatologists studied images taken by these satellites 2-3 years before the disaster and photographs over the past year, and also made several expeditions to that part of western Antarctica, where, according to their assumptions, the reason for the formation of this iceberg was located.
According to climatologists, a simple trick often used by professional photographers helped them in this search - they studied and analyzed only those photographs that satellites received at sunset and dawn, when the Sun is almost at the horizon, and its rays fall at a large angle to the surface of Antarctica .
This allowed scientists to achieve maximum image contrast and find the reason for the formation of a mega-iceberg - two giant cracks in the Western Ice Sheet, going to a great depth inside the ice mass towards the central part of this ice mass.
Both of these faults, as further analysis of the data showed, arose about two and three years ago in that part of the glacier that is located at the border between water, land and ice, at the very base of the Western Ice Sheet. Emerging at the end of 2013 and 2014, both of these fissures grew rapidly, each year increasing in length by about 14 kilometers, and expanding their width by about 110 meters.
The reason for the birth of this crack, according to scientists, is an increase in the temperature of the sea, the waters of which constantly wash the lower part of the glacier. A similar process, according to Howat and his colleagues, led to the formation of a kind of “cavity” in the part of the glacier where these cracks were born, and ultimately, this void caused the glacier to literally fall into itself, giving rise to a giant crack. Similar processes, Howat and his colleagues found last year, are also accelerating the melting of Greenland's glaciers.
“The most worrying thing is that similar “valleys” exist in other parts of the ice mass, located even further inland. If the ice in them is weakened and cracks appear, then the rate of destruction of the glaciers of Antarctica and their “escape” into the ocean will accelerate,” - concludes the scientist.
This I know
1. Tell us about the geographical location of Antarctica. What oceans surround the mainland? What currents run along its banks?
The territory of Antarctica is almost entirely located within the southern polar circle. The mainland is located in three hemispheres at once - Southern, Eastern and Western. The mainland is washed by the Pacific, Indian and Atlantic oceans. Around Antarctica is the most powerful current of the Western winds.
2. What are ice shelves? How are icebergs formed?
Ice shelves - ice that covers not only the mainland, but also slides tongues onto the adjacent seas and islands.
Icebergs are formed when huge chunks of ice break off from an ice shelf.
3. What are katabatic winds and what causes them to form?
An area of constant strong cooling is forming over Antarctica due to the glacier. As a result, an area of high pressure is formed over the mainland. Masses of cold air flow down from the center to the outskirts, forming the strongest katabatic winds.
4. When does summer begin in Antarctica? Winter?
Antarctica lies entirely in the Southern Hemisphere. Therefore, summer comes from the day of the winter solstice (December 21), winter - from the day of the summer solstice (June 22).
5. Why are there negative temperatures in Antarctica all year round?
Negative temperatures throughout the year are associated with the position of the mainland beyond the Arctic Circle. The angle of incidence of the sun's rays is very small. In addition, snow and ice cover reflects more of the sun's rays back into the atmosphere, so the earth's surface does not warm up.
This I can
7. Consider the profile of the structure of Antarctica (see Fig. 105). Make a conclusion about the structure of Ice Antarctica and the relief of Stone Antarctica?
The relief of Stony Antarctica is characterized by very small absolute heights, small elevation differences. Icy Antarctica has the shape of a dome. A powerful ice cover has a huge mass. Plastic ice masses flow down from the center to the periphery, forming a convex shape. Icy Antarctica is the highest continent.
8. Consider the photo in fig. 107. How have penguins adapted to life in harsh conditions?
The plumage of penguins is different than that of other birds: feathers are small, hard, dense, similar to scales, fat accumulates under the skin of penguins. Penguins cannot fly, but they are excellent swimmers, which helps them get food in the ocean. Penguins live in large groups. During snowstorms, they warm up by becoming close to each other and constantly moving from the edge to the center.
It's interesting to me
9. Prepare a message on the topic "How Antarctica was discovered."
How Antarctica was discovered
The initial stage is the discovery of islands around Antarctica and the search for the mainland (16th century - early 19th century)
Long before the discovery of the mainland, various assumptions were made about the existence of a hypothetical Southern land, in search of which expeditions were sent to discover large islands around Antarctica. In 1768-71, J. Cook led an expedition that was heading in search of the southern mainland. Having examined New Zealand, the expedition discovered the strait between its North and South Islands (later named after Cook) and found that New Zealand is not a protrusion of the southern mainland, as previously thought, but an archipelago of two islands. In 1772-75, Cook, on the second expedition dedicated to the search for the southern mainland, was the first of the navigators to cross the Antarctic Circle, but he did not find the mainland and stated that it was impossible to find it at all because of the ice that made the land inaccessible.
The second stage - the discovery of Antarctica and the first scientific research (19th century)
The discovery of Antarctica as an icy continent belongs to the Russian round-the-world naval expedition led by F. F. Bellingshausen and M. P. Lazarev on the sloops Vostok and Mirny. In January-February 1820, Russian ships approached the Queen Maud Land ice shelf four times at close range. Russian expedition discovered about. Peter I, Alexander I Land and several islands in the South Shetland archipelago. In 1820-1821, English and American animal industry ships (headed by E. Bransfield and N. Palmer) were close to the Antarctic Peninsula (Graham Land). The voyage around Antarctica and the discovery of Enderby Land, Adelaide and Biscoe Islands was made in 1831-33 by the English navigator J. Biscoe. Three scientific expeditions visited Antarctica in 1838-42: French (J. Dumont-Durville), American (C. Wilks), and English (J. Ross). The first discovered Louis Philippe Land, Joinville Land, Adélie Land and Clary Land (landed on coastal cliffs for the first time), the second - Wilkes Land, the third - Victoria Land, coastal islands, and also for the first time passed along the giant Ross Ice Shelf, calculated the location of the South Magnetic Pole .
After these voyages, a fifty-year period of calm set in in Antarctica. Interest in Antarctica increased at the end of the 19th century. due to the fact that due to predatory extermination, the number of whales in the Arctic has decreased. Several expeditions visited Antarctica: the Scottish one on the Valena ship, which discovered Oscar II Land, later so named by the Norwegian expedition on the Jason and Antarctica; the latter discovered the Larsen Coast and landed on the coast of Antarctica in the area of Cape Adare; the Belgian under the leadership of Antarctica Gerlache, wintering in Antarctica on the drifting ship "Belgica", and the English on the "Southern Cross", organizing wintering at Cape Adare (the beginning of wintering K. Borchgrevink).
The third stage is the study of the coast and inland regions of Antarctica (first half of the 20th century)
At the beginning of the 20th century, expeditions to the polar mountain ranges and glaciers of the mainland began one after another. Preparations begin to reach the South Pole of the planet. In 1909, the Norwegian Roald Amundsen is preparing for this very difficult and dangerous crossing of the icy continent. On January 14, 1911, the Norwegians landed on the coast of Antarctica in the Bay of Whales. Together with them, an British expedition led by Robert Scott set off to conquer the pole, arriving in Antarctica a few days earlier - on January 3rd. Amundsen's proposed route was 100 kilometers shorter than Scott's, however, he ran through more difficult terrain. But Amundsen calculated all the stages of the campaign with amazing accuracy. Between 80° and 85° every degree he set up warehouses with food and fuel, and to make them easy to find, he set up high milestones with flags. Amundsen's campaign began on October 20, 1911 with four comrades on a sleigh pulled by dogs. Beyond the 85th parallel, a heavy ascent began from the Ross Ice Shelf to the ridge, named by Amundsen in honor of the Norwegian queen, the Queen Maud ridge (later it was proved that this ridge belongs to the Transantarctic Mountains). When part of the food was already over, Amundsen ordered to kill extra dogs in order to feed them with the meat of other animals, however, the travelers themselves ate this meat, because the provisions were running out. The Norwegian expedition reached the South Pole on December 15, 1911. They pitched a tent on a high plateau, 2800 meters high, and raised the Norwegian flag there. Roald Amundsen and his companions became the first people to conquer the South Pole. On December 17 they turned north. They had to kill one dog every three days, so people and animals ate fresh meat until they reached the 85th parallel, where the first of the warehouses they left was located. Having traveled 2800 km both ways, they returned to Whale Bay on January 26, 1912 after a 99-day ice voyage.
At this time, Robert Scott planned to get to the pole on a motor sleigh, Indian ponies and dogs. They set off on November 2, 1911. However, the technique failed Scott, the motor sled soon had to be abandoned, and the ponies had to be killed beyond the 83rd parallel when there was nothing to feed them. Dog teams were sent back at 84°, and the British themselves pulled the heavily laden sledges. Beyond the 85th parallel, Scott ordered four people to return, and at 87°30' another three. Only five people went further: Robert Scott, doctor Edward Wilson, officers Lawrence Oates and Henry Bowers, and non-commissioned officer Edgar Evans (pictured). The last 250 km were given to them especially hard. The sleigh had to be dragged through dry, loose snow, moving no more than 2 km per hour, and moving less than 10 km in a day. When the Pole was a few miles away, Scott wrote in his diary: “...saw a black dot ahead... [turned out to be] a black flag tied to a sledge run. The remnants of the camp were immediately visible nearby ... The Norwegians were ahead of us. They were the first to reach the Pole. Terrible disappointment!" On the way from their base to the Pole, the British set up ten intermediate depots of provisions and fuel. On the way back, their immediate goal was to get to the next warehouse as soon as possible in order to renew their fuel and fuel supplies. However, the strength of travelers quickly dwindled. Soon the youngest of them, Evans, began to feel signs of mental illness, he lagged behind, fell until he was completely exhausted. On February 17, he passed away. The way forward was even more difficult. Scott's team went astray more and more often. At the end of February, when "fuel became terribly scarce," severe frosts began. Scott's notes showed how their will to live was fading, and their despair was growing. But until the very end, they did not quit and dragged about 15 kilograms of the most valuable rock samples collected on the way to the pole. Friday 16 March or Saturday 17 March, Scott wrote in his diary: “Lost count of numbers, but the last one seems to be true. Our life is pure tragedy. Ots said, “I'll go for a walk. Maybe I won't be back soon." He went into a snowstorm, and we never saw him again ... we knew that ... Ots was going to his death, and dissuaded him, but ... realized that he was acting like a noble person ... ". March 29: “From the 21st a continuous storm raged… On the 20th we had fuel for two cups of tea each and two days of dry food. Every day we were ready to go… but there was no way to get out of the tent – the snow carried and twisted like that. I don’t think we can hope for anything else now…” Robert Scott's last entry: "For God's sake, don't leave our loved ones." The search party found their snow-covered tent only in the spring - November 12, 1912. All the travelers of Scott's expedition died, he himself was the last to die, discarding the lapels of his sleeping bag and unbuttoning his jacket. This is where they were buried. On the memorial cross, set in the ice in memory of the expedition, an epitaph was carved: “To strive, to seek, to find, and not to yield”. The whole of Great Britain was deeply distressed by the news of the death of its heroes. It is worth saying that Scott's last request found a response in the hearts of the British and was fulfilled. A significant amount collected throughout the country ensured a comfortable existence for the relatives of the dead travelers.
After the conquest of the South Pole by Amundsen and Scott, Antarctic exploration continued with renewed vigor. In December 1911, Douglas Mawson made his first expedition. For wintering, his expedition chose Adélie Land, as it turned out, the place with the most severe climate on Earth. Often the average daily winds here reached a speed of 44 m/s. Mawson had to observe winds of 90 m/s when the speed of a devastating hurricane was only 30 m/s. To all this was added the largest amount of precipitation in Antarctica - 1600 mm per year. The campaign of 1912-1913 almost became fatal for Mawson himself, his entire team died, and he himself returned to the base only five months later. However, during the expedition, the discoveries of Charles Wilks were confirmed, vast territories were explored, and the description of the information collected amounted to 22 volumes. In the 1920s, flights over Antarctica began to be made, which made it possible to explore the mountains and lands in the depths of the continent. Among the researchers of this time, it is necessary to mention the American pilot Richard Byrd, the Norwegian captain Nils Larsen, the American engineer Lincoln Ellsworth.
The first Soviet Antarctic scientific expedition under the command of an experienced polar explorer and oceanologist Mikhail Mikhailovich Somov landed on the coast of the Davis Sea on January 6, 1956. Nearby, with the help of the crews of two diesel-electric ships "Ob" and "Lena", the village of Mirny was built. Antarctic sector between 80° and 105° E was not chosen by chance. The coast of the mainland was mapped very approximately; in the course of the work of Soviet researchers, many new islands, bays, capes and glaciers were discovered. In addition to the base in the village of Mirny, by the end of 1956, two more stations arose: Pionerskaya and Oasis station.
There are currently 37 stations in Antarctica. Argentina is actively developing the mainland, which has 6 stations here. After the collapse of the USSR and the resulting economic difficulties, Russia was forced to freeze some of them. Now there are 5 Russian stations on the mainland: "Bellingshausen" (62°12"S 58°56"W), "Vostok" (78°27"S 106°52"E). ), "Mirny" (66°33"S 93°01"E), "Novolazarevskaya" (70°46"S 11°50"E), "Progress" ( 69°23" S 76°23" E) – (Data from the Russian Antarctic Expedition: USA, Australia and Chile have 3 stations each on the mainland. Great Britain and China have two stations each. Also, one station each has: Norway, France, New Zealand, Japan, Brazil, Uruguay, South Korea, South Africa, Germany, India, Poland, Ukraine There is also one joint station between France and Italy.
Since 1961, there has been an agreement signed by all leading countries, according to which the territories south of 60 ° S. are demilitarized and free of nuclear weapons. Also, no country in the world has the right to claim these territories. It provides for freedom of scientific research and encourages international cooperation to ensure that Antarctica is used for the benefit of all mankind.
What are the reasons for the formation of glaciers in Antarctica?
A study by University of Massachusetts geoscientist Robert DeConto has established an alternative theory of why Antarctica was suddenly covered in glaciers 34 million years ago. His theory challenges previous ideas about ice formation.
DeConto, in collaboration with David Pollard of Pennsylvania State University, published their findings in the Jan. 16 issue of the journal Nature. His work was funded by the National Science Foundation.
Scientists have known for a long time that Antarctica was not always covered with layers of many kilometers of ice. Once this continent was covered with green vegetation and dinosaurs walked on it,” says Deconto. “It is believed that Antarctica, which was then part of a single continent from the continents - Pangea, was a temperate zone with a tropical forest.
Previous studies of microremains and ocean chemistry have already shown that Antarctic ice formed very quickly - within 50,000 years or even less. Dramatic climate change occurred during the Oligocene and Eocene eras. It remains a mystery - why did this happen and why so quickly?
A theory put forward in the 1970s suggested that plate tectonics was the driving force in the Antarctic freeze. Pangea was breaking apart. Australia moved northward, opening up an ocean channel known as the Tasmanian Passage. And the scientists concluded that as South America drifted away from Antarctica, the Drake Passage opened up. This was thought to be the last barrier to the oceanic current circumventing the entire continent. This current diverted the warmer northern waters and served to keep the continent cool and the southern ocean waters cool. This theory was known as "Thermal Insulation".
DeConto and Pollard set out to determine how important the discovery of southern ocean currents was to the rapid freezing of Antarctica. Among the factors they considered: ocean currents; plate tectonics; the content of carbon dioxide in the atmosphere; and changes in the Earth's orbital parameters.
Using computer simulations, scientists have essentially reconstructed a picture of the world 34 million years ago, including the detailed topography of Antarctica and the placement of drifting continents. The topography was especially important, because if there are many mountains, they can serve as a very good catalyst to build up glaciers even in summer.
The study showed that the critical factor in the rapid cooling of the continent and its ice cover was not the discovery of new ocean currents, but a change in the carbon dioxide content in the atmosphere.
Carbon dioxide is a very important component that affects climate change. Current global warming and rising levels of CO2 in the atmosphere may mean that the Antarctic ice will melt very quickly.
