Quaternary period of the Cenozoic era: animals, plants, climate. Periods of the geological history of the Earth. Ice Age. Ice Age When will the Ice Age start on Earth?

The Ice Age has always been a mystery. We know that he could shrink entire continents to the size of a frozen tundra. We know there have been eleven or so, and they seem to happen on a regular basis. We definitely know that there was a lot of ice. However, there is much more to the ice ages than meets the eye.

By the time the last ice age arrived, evolution had already “invented” mammals. The animals that decided to breed and multiply during the Ice Age were quite large and covered in fur. Scientists have given them the common name "megafauna" because they managed to survive the Ice Age. However, since other, less cold-resistant species could not survive it, the megafauna felt pretty good.

Megafauna herbivores are accustomed to foraging in icy environments, adapting to their environment in a variety of ways. For example, Ice Age rhinoceroses may have had a shovel-shaped horn to remove snow. Predators like saber-toothed tigers, short-faced bears, and direwolves (yes, Game of Thrones wolves did once exist) have also adapted to their environment. Although the times were cruel, and the prey could well turn a predator into a prey, there was a lot of meat in it.

ice age people

Despite their relatively small size and little hair, Homo sapiens survived in the cold tundras of the ice ages for thousands of years. Life was cold and hard, but people were resourceful. For example, 15,000 years ago, people of the Ice Age lived in tribes of hunter-gatherers, built comfortable dwellings from mammoth bones and made warm clothes from animal fur. When food was plentiful, they stored it in natural permafrost refrigerators.

Since hunting tools at that time were mainly stone knives and arrowheads, complex weapons were rare. To capture and kill huge ice age animals, people used traps. When an animal fell into a trap, people attacked it in a group and beat it to death.

Little Ice Ages

Sometimes small ice ages arose between large and long ones. They were not as destructive, but could still cause starvation and disease due to failed crops and other side effects.

The most recent of these small ice ages began sometime between the 12th and 14th centuries and peaked between 1500 and 1850. For hundreds of years, the weather in the northern hemisphere was damn cold. In Europe, the seas regularly froze over, and mountainous countries (such as Switzerland) could only watch as glaciers moved, destroying villages. There were years without a summer, and nasty weather conditions affected every aspect of life and culture (perhaps this is why the Middle Ages seem gloomy to us).

Science is still trying to figure out what caused this little ice age. Possible causes include a combination of heavy volcanic activity and a temporary decrease in solar energy from the Sun.

warm ice age

Some ice ages may have been quite warm. The ground was covered with a huge amount of ice, but in fact the weather was quite pleasant.

Sometimes the events that lead to an ice age are so severe that even if full of greenhouse gases (which trap the sun's heat in the atmosphere, warming the planet), ice still continues to form because, given a thick enough layer of pollution, it will reflect the sun's rays back into space. Experts say this would turn Earth into a giant Baked Alaska dessert - cold on the inside (ice on the surface) and warm on the outside (warm atmosphere).

The man whose name is reminiscent of the famous tennis player was actually a respected scientist, one of the geniuses who defined the scientific environment of the 19th century. He is considered one of the founding fathers of American science, although he was French.

In addition to many other achievements, it is thanks to Agassiz that we know at least something about the ice ages. Although many have touched on this idea before, in 1837 the scientist became the first person to seriously bring ice ages into science. His theories and publications on the ice fields that covered most of the earth were foolishly dismissed when the author first presented them. Nevertheless, he did not retract his words, and further research eventually led to the recognition of his "crazy theories."

Remarkably, his pioneering work on ice ages and glacial activity was merely a hobby. By occupation, he was an ichthyologist (studying fish).

Man-made pollution prevented the next ice age

Theories that ice ages repeat on a semi-regular basis, no matter what we do, often clash with theories about global warming. While the latter are certainly authoritative, some believe that it is global warming that may be useful in the future fight against glaciers.

Human-caused carbon dioxide emissions are considered an essential part of the global warming problem. However, they have one strange side effect. According to researchers from the University of Cambridge, CO2 emissions may be able to stop the next ice age. How? Although the planetary cycle of the Earth is constantly trying to start an ice age, it will only start if the level of carbon dioxide in the atmosphere is extremely low. By pumping CO2 into the atmosphere, humans may have accidentally made ice ages temporarily unavailable.

And even if the concern about global warming (which is also extremely bad) forces people to reduce their CO2 emissions, there is still time. At present, we have sent so much carbon dioxide into the sky that the ice age will not start for at least another 1000 years.

Plants of the Ice Age

It was relatively easy for predators during the ice ages. After all, they could always eat someone else. But what did herbivores eat?

It turns out that everything you wanted. In those days, there were many plants that could have survived the Ice Age. Even in the coldest times, steppe-meadow and tree-shrub areas remained, which allowed mammoths and other herbivores not to die of hunger. These pastures were full of plant species that thrive in cold, dry weather, such as spruces and pines. In warmer areas, birches and willows were abundant. In general, the climate at that time was very similar to Siberian. Although the plants, most likely, were seriously different from their modern counterparts.

All of the above does not mean that the ice ages did not destroy part of the vegetation. If the plant could not adapt to the climate, it could only migrate through the seeds or disappear. Australia once had the longest list of diverse plants until glaciers wiped out a good part of them.

The Himalayas may have caused an ice age

Mountains, as a rule, are not famous for actively causing anything but occasional landslides - they just stand there and stand. The Himalayas can refute this belief. Perhaps they are directly responsible for causing the Ice Age.

When the landmasses of India and Asia collided 40-50 million years ago, the collision grew massive rock ridges into the Himalaya mountain range. This brought out a huge amount of "fresh" stone. Then the process of chemical erosion began, which removes a significant amount of carbon dioxide from the atmosphere over time. And this, in turn, could affect the climate of the planet. The atmosphere "cooled" and caused an ice age.

snowball earth

During most ice ages, ice sheets cover only part of the world. Even a particularly severe ice age covered, as they say, only about one third of the globe.

What is "Snowball Earth"? The so-called Snowball Earth.

Snowball Earth is the chilling grandfather of the ice ages. This is a complete freezer that literally froze every part of the planet's surface until the Earth froze into a huge snowball flying in space. The few that survived a complete freeze either clung to rare places with relatively little ice, or, in the case of plants, clung to places where there was enough sunlight for photosynthesis.

According to some reports, this event happened at least once, 716 million years ago. But there could be more than one such period.

garden of eden

Some scientists seriously believe that the Garden of Eden was real. They say he was in Africa and was the only reason our ancestors survived the Ice Age.

Just under 200,000 years ago, a particularly hostile ice age was killing species left and right. Fortunately, a small group of early humans were able to survive the terrible cold. They stumbled upon the coast that is now represented by South Africa. Despite the fact that ice was reaping its share all over the world, this area remained ice-free and completely habitable. Her soil was rich in nutrients and provided plenty of food. There were many natural caves that could be used as shelter. For a young species struggling to survive, it was nothing short of heaven.

The human population of the "Garden of Eden" numbered only a few hundred individuals. This theory is supported by many experts, but it still lacks conclusive evidence, including studies that show that humans have much less genetic diversity than most other species.

Russian scientists promise that in 2014 the world will begin an ice age. Vladimir Bashkin, head of the Gazprom VNIIGAZ laboratory, and Rauf Galiullin, researcher at the Institute for Fundamental Problems of Biology of the Russian Academy of Sciences, argue that there will be no global warming. According to scientists, warm winters are the result of cyclical activity of the sun and cyclical climate change. This warming has continued from the 18th century to the present, and next year the Earth will begin to cool again.

The Little Ice Age will begin gradually and last at least two centuries. The decrease in temperature will reach its peak by the middle of the 21st century.

At the same time, scientists say that the anthropogenic factor - human impact on the environment - does not play such a big role in climate change as is commonly thought. Business in marketing, Bashkin and Galiullin consider, and the promise of cold weather every year is only a way to inflate the price of fuel.

Pandora's Box - The Little Ice Age in the 21st century.

In the next 20-50 years, we are threatened by the Little Ice Age, because it has already happened before and must come again. Researchers believe that the onset of the Little Ice Age was associated with a slowdown in the Gulf Stream around 1300. In the 1310s, Western Europe, judging by the chronicles, experienced a real ecological catastrophe. According to the French Chronicle of Matthew of Paris, the traditionally warm summer of 1311 was followed by four gloomy and rainy summers of 1312-1315. Heavy rains and unusually harsh winters have killed several crops and frozen orchards in England, Scotland, northern France and Germany. Viticulture and wine production ceased in Scotland and northern Germany. Winter frosts began to hit even northern Italy. F. Petrarch and J. Boccaccio recorded that in the XIV century. snow often fell in Italy. A direct consequence of the first phase of the MLP was the massive famine in the first half of the 14th century. Indirectly - the crisis of the feudal economy, the resumption of corvee and major peasant uprisings in Western Europe. In the Russian lands, the first phase of the MLP made itself felt in the form of a series of “rainy years” of the 14th century.

From about the 1370s, temperatures in Western Europe began to rise slowly, and massive famine and crop failures ceased. However, cold, rainy summers were a frequent occurrence throughout the 15th century. In winter, snowfalls and frosts were often observed in southern Europe. Relative warming began only in the 1440s, and it immediately led to the rise of agriculture. However, the temperatures of the previous climatic optimum have not been restored. For Western and Central Europe, snowy winters became commonplace, and the period of "golden autumn" began in September.

What is it that affects the climate? Turns out it's the sun! Back in the 18th century, when sufficiently powerful telescopes appeared, astronomers drew attention to the fact that the number of sunspots on the Sun increases and decreases with a certain periodicity. This phenomenon is called cycles of solar activity. They also found out their average duration - 11 years (the Schwabe-Wolf cycle). Later, longer cycles were discovered: a 22-year (Hale cycle) associated with a change in the polarity of the solar magnetic field, a "secular" Gleissberg cycle lasting about 80-90 years, and a 200-year (Süss cycle). It is believed that there is even a cycle of 2400 years.

"The fact is that longer cycles, for example, secular ones, modulating the amplitude of the 11-year cycle, lead to the emergence of grandiose minima," said Yury Nagovitsyn. There are several known to modern science: the Wolf minimum (early 14th century), the Sperer minimum (second half of the 15th century) and the Maunder minimum (second half of the 17th century).

Scientists have suggested that the end of the 23rd cycle, in all likelihood, coincides with the end of the secular cycle of solar activity, the maximum of which was in 1957. This, in particular, is evidenced by the curve of relative Wolf numbers, which has approached its minimum mark in recent years. Indirect evidence of the superposition is the delay of the 11-year-old. Comparing the facts, scientists realized that, apparently, a combination of factors indicates an approaching grandiose minimum. Therefore, if in the 23rd cycle the activity of the Sun was about 120 relative Wolf numbers, then in the next it should be about 90-100 units, astrophysicists suggest. Further activity will decrease even more.

The fact is that longer cycles, for example, secular ones, modulating the amplitude of the 11-year cycle, lead to the appearance of grandiose minima, the last of which occurred in the 14th century. What are the consequences for the Earth? It turns out that it was during the grandiose maxima and minima of solar activity on Earth that large temperature anomalies were observed.

The climate is a very complicated thing, it is very difficult to track all its changes, all the more so on a global scale, but as scientists suggest, the greenhouse gases that bring the vital activity of mankind slowed down the arrival of the Little Ice Age a little, besides, the world ocean, having accumulated part of the heat over the past decades, also delays the process the beginning of the Little Ice Age, giving off a little bit of its heat. As it turned out later, vegetation on our planet absorbs excess carbon dioxide (CO2) and methane (CH4) well. The main influence on the climate of our planet is still exerted by the Sun, and we cannot do anything about it.

Of course, nothing catastrophic will happen, but in this case, part of the northern regions of Russia may become completely unsuitable for life, oil production in the north of the Russian Federation may cease altogether.

In my opinion, the beginning of a decrease in global temperature can already be expected in 2014-2015. In 2035-2045, the solar luminosity will reach a minimum, and after that, with a delay of 15-20 years, the next climate minimum will come - a deep cooling of the Earth's climate.

News about the end of the world » The Earth is threatened by a new ice age.

Scientists predict a decline in solar activity that may occur over the next 10 years. The consequence of this may be a repetition of the so-called "Little Ice Age", which happened in the XVII century, writes Times.

According to scientists, the frequency of sunspots in the coming years may decrease significantly.

The cycle of formation of new sunspots that affect the temperature of the Earth is 11 years. However, employees of the American National Observatory suggest that the next cycle may be very late or not happen at all. According to the most optimistic forecasts, they argue, a new cycle could begin in 2020-21.

Scientists are speculating whether the change in solar activity will lead to a second "Maunder Low" - a period of sharp decline in solar activity that lasted 70 years, from 1645 to 1715. During this time, also known as the "Little Ice Age", the river Thames was covered with nearly 30 meters of ice, on which horse-drawn cabs successfully traveled from Whitehall to London Bridge.

According to researchers, the decline in solar activity can lead to the fact that the average temperature on the planet will drop by 0.5 degrees. However, most scientists believe that it is too early to sound the alarm. During the "Little Ice Age" in the XVII century, the air temperature dropped significantly only in the north-west of Europe, and even then only by 4 degrees. On the rest of the planet, the temperature dropped by only half a degree.

The Second Coming of the Little Ice Age

In historical time, Europe has already once experienced a prolonged anomalous cooling.

Abnormally severe frosts that reigned in Europe at the end of January almost led to a full-scale collapse in many Western countries. Due to heavy snowfalls, many highways were blocked, power supply was interrupted, and aircraft reception at airports was canceled. Due to frost (in the Czech Republic, for example, reaching -39 degrees), classes in schools, exhibitions and sports matches are canceled. In the first 10 days of extreme frosts in Europe alone, more than 600 people died from them.

For the first time in many years, the Danube froze from the Black Sea to Vienna (the ice there reaches 15 cm thick), blocking hundreds of ships. To prevent the freezing of the Seine in Paris, an icebreaker that had long been idle was launched into the water. Ice has blocked the canals of Venice and the Netherlands; in Amsterdam, skaters and cyclists ride on its frozen waterways.

The situation for modern Europe is extraordinary. However, looking at the famous works of European art of the 16th-18th centuries or in the records of the weather of those years, we learn that the freezing of canals in the Netherlands, the Venetian lagoon or the Seine was a rather frequent phenomenon for that time. The end of the 18th century was especially extreme.

Thus, the year 1788 was remembered by Russia and Ukraine as the "great winter", accompanied throughout their European part by "extraordinary cold, storms and snow". In Western Europe in December of the same year, a record temperature of -37 degrees was recorded. Birds froze on the fly. The Venetian lagoon froze over, and the townspeople skated along its entire length. In 1795, the ice bound the shores of the Netherlands with such force that an entire military squadron was captured in it, which was then surrounded by ice from land by a French cavalry squadron. In Paris that year, frosts reached -23 degrees.

Paleoclimatologists (historians studying climate change) call the period from the second half of the 16th century to the beginning of the 19th century the “Little Ice Age” (A.S. Monin, Yu.A. epoch" (E. Le Roy Ladurie "History of climate since 1000". L., 1971). They note that during that period there were not individual cold winters, but in general a decrease in temperature on Earth.

Le Roy Ladurie analyzed data on the expansion of glaciers in the Alps and the Carpathians. He points to the following fact: the gold mines developed in the middle of the 15th century in the High Tatras in 1570 were covered with ice 20 m thick, in the 18th century the thickness of the ice there was already 100 m. By 1875, despite the widespread retreat throughout the 19th century and the melting of glaciers, the thickness of the glacier over the medieval mines in the High Tatras was still 40 m. At the same time, as the French paleoclimatologist notes, the onset of glaciers began in the French Alps. In the commune of Chamonix-Mont-Blanc, in the mountains of Savoy, "the advance of the glaciers definitely began in 1570-1580."

Le Roy Ladurie gives similar examples with exact dates in other places in the Alps. In Switzerland, evidence of the expansion of a glacier in the Swiss Grindelwald dates back to 1588, and in 1589 a glacier descended from the mountains blocked the valley of the Saas River. In the Pennine Alps (in Italy near the border with Switzerland and France) in 1594–1595, a noticeable expansion of glaciers was also noted. “In the Eastern Alps (Tyrol, etc.), glaciers advance in the same way and simultaneously. The first information about this dates back to 1595, writes Le Roy Ladurie. And he adds: “In 1599-1600, the glacier development curve reached its peak for the entire region of the Alps.” Since that time, endless complaints from the inhabitants of mountain villages have appeared in written sources that glaciers are burying their pastures, fields and houses under them, thus erasing entire settlements from the face of the earth. In the XVII century, the expansion of glaciers continues.

This is consistent with the expansion of glaciers in Iceland, starting from the end of the 16th century and throughout the 17th century advancing on settlements. As a result, Le Roy Ladurie states, “Scandinavian glaciers, synchronously with Alpine glaciers and glaciers from other regions of the world, have been experiencing the first, well-defined historical maximum since 1695,” and “in subsequent years they will begin to advance again.” This continued until the middle of the 18th century.

The thickness of the glaciers of those centuries can indeed be called historical. On the graph of changes in the thickness of glaciers in Iceland and Norway over the past 10 thousand years, published in the book by Andrey Monin and Yuri Shishkov "The History of Climate", it is clearly seen how the thickness of glaciers, which began to grow around 1600, by 1750 reached the level at which the glaciers kept in Europe during the period of 8-5 thousand years BC.

Is it any wonder that since the 1560s, contemporaries have recorded in Europe over and over again extraordinarily cold winters, which were accompanied by the freezing of large rivers and reservoirs? These cases are indicated, for example, in the book by Yevgeny Borisenkov and Vasily Pasetsky “A Millennial Chronicle of Unusual Natural Phenomena” (M., 1988). In December 1564, the powerful Scheldt in the Netherlands completely froze over and stood under the ice until the end of the first week of January 1565. The same cold winter was repeated in 1594/95, when the Scheldt and the Rhine froze over. The seas and straits froze: in 1580 and 1658 - the Baltic Sea, in 1620/21 - the Black Sea and the Bosphorus Strait, in 1659 - the Great Belt Strait between the Baltic and North Seas (the minimum width of which is 3.7 km).

The end of the 17th century, when, according to Le Roy Ladurie, the thickness of glaciers in Europe reaches a historical maximum, was marked by crop failures due to prolonged severe frosts. As noted in the book by Borisenkov and Pasetsky: “The years 1692-1699 were marked in Western Europe by continuous crop failures and hunger strikes.”

One of the worst winters of the Little Ice Age occurred in January-February 1709. Reading the description of those historical events, you involuntarily try them on modern ones: “From an extraordinary cold, such as neither grandfathers nor great-grandfathers remembered ... the inhabitants of Russia and Western Europe died. Birds flying through the air froze. In general, in Europe, many thousands of people, animals and trees died. In the vicinity of Venice, the Adriatic Sea was covered with stagnant ice. The coastal waters of England were covered with ice. Frozen Seine, Thames. The ice on the Meuse River reached 1.5 m. The frosts were just as great in the eastern part of North America. The winters of 1739/40, 1787/88 and 1788/89 were no less severe.

In the 19th century, the Little Ice Age gave way to warming and harsh winters are a thing of the past. Is he coming back now?

The consequences of warming

The last ice age brought about the appearance of the woolly mammoth and a huge increase in the area of ​​glaciers. But it was only one of many that have cooled the Earth throughout its 4.5 billion years of history.

So, how often does the planet go through ice ages, and when should we expect the next one?

The main periods of glaciation in the history of the planet

The answer to the first question depends on whether you mean the big glaciations or the small ones that occur during these long periods. Throughout history, the Earth has experienced five major glaciations, some of them lasting hundreds of millions of years. In fact, even now, the Earth is going through a large period of glaciation, and this explains why it has polar ice.

The five main ice ages are the Huronian (2.4-2.1 billion years ago), the Cryogenian glaciation (720-635 million years ago), the Andean-Saharan (450-420 million years ago), the late Paleozoic glaciation (335-260 million years ago) and the Quaternary (2.7 million years ago to the present).

These major periods of glaciation may alternate between smaller ice ages and warm periods (interglacials). At the beginning of the Quaternary glaciation (2.7-1 million years ago), these cold ice ages occurred every 41,000 years. However, in the last 800,000 years, significant ice ages have appeared less frequently - about every 100,000 years.

How does the 100,000 year cycle work?

Ice sheets grow for about 90,000 years and then begin to melt during the 10,000 year warm period. Then the process is repeated.

Given that the last ice age ended about 11,700 years ago, perhaps it's time for another one to begin?

Scientists believe that we should be experiencing another ice age right now. However, there are two factors associated with the Earth's orbit that influence the formation of warm and cold periods. Considering how much carbon dioxide we emit into the atmosphere, the next ice age won't start for at least another 100,000 years.

What causes an ice age?

The hypothesis put forward by the Serbian astronomer Milyutin Milanković explains why there are cycles of ice and interglacial periods on Earth.

As a planet revolves around the Sun, the amount of light it receives from it is affected by three factors: its tilt (which ranges from 24.5 to 22.1 degrees in a 41,000-year cycle), its eccentricity (changing the shape of its orbit around of the Sun, which fluctuates from a near circle to an oval shape) and its wobble (one complete wobble occurs every 19-23 thousand years).

In 1976, a landmark paper in the journal Science presented evidence that these three orbital parameters explained the planet's glacial cycles.

Milankovitch's theory is that orbital cycles are predictable and very consistent in a planet's history. If the Earth is going through an ice age, then it will be covered in more or less ice, depending on these orbital cycles. But if the Earth is too warm, no change will occur, at least in regards to the growing amount of ice.

What can affect the warming of the planet?

The first gas that comes to mind is carbon dioxide. Over the past 800,000 years, carbon dioxide levels have fluctuated between 170 and 280 parts per million (meaning that out of 1 million air molecules, 280 are carbon dioxide molecules). A seemingly insignificant difference of 100 parts per million leads to the appearance of glacial and interglacial periods. But carbon dioxide levels are much higher today than they were in past fluctuations. In May 2016, carbon dioxide levels over Antarctica reached 400 parts per million.

The earth has warmed up so much before. For example, during the time of the dinosaurs, the air temperature was even higher than now. But the problem is that in the modern world it is growing at a record pace, because we have released too much carbon dioxide into the atmosphere in a short time. In addition, given that emission rates are not declining to date, it can be concluded that the situation is unlikely to change in the near future.

The consequences of warming

The warming caused by the presence of this carbon dioxide will have big consequences, because even a small increase in the average temperature of the Earth can lead to drastic changes. For example, the Earth was on average only 5 degrees Celsius colder during the last ice age than it is today, but this has led to a significant change in regional temperature, the disappearance of a huge part of the flora and fauna, and the appearance of new species.

If global warming causes all of the ice sheets in Greenland and Antarctica to melt, ocean levels will rise by 60 meters compared to today.

What causes great ice ages?

The factors that caused long periods of glaciation, such as the Quaternary, are not as well understood by scientists. But one idea is that a massive drop in carbon dioxide levels could lead to cooler temperatures.

So, for example, according to the uplift and weathering hypothesis, when plate tectonics leads to the growth of mountain ranges, new unprotected rock appears on the surface. It is easily weathered and disintegrates when it enters the oceans. Marine organisms use these rocks to create their shells. Over time, stones and shells take carbon dioxide from the atmosphere and its level drops significantly, which leads to a period of glaciation.

In the history of the Earth, there were long periods when the entire planet was warm - from the equator to the poles. But there were also times so cold that glaciations reached those regions that currently belong to the temperate zones. Most likely, the change of these periods was cyclical. During warmer times, there could be relatively little ice, and it was only in the polar regions or on the tops of mountains. An important feature of ice ages is that they change the nature of the earth's surface: each glaciation affects the appearance of the Earth. By themselves, these changes may be small and insignificant, but they are permanent.

History of Ice Ages

We do not know exactly how many ice ages there have been throughout the history of the Earth. We know of at least five, possibly seven, ice ages, starting with the Precambrian, in particular: 700 million years ago, 450 million years ago (Ordovician), 300 million years ago - Permo-Carboniferous glaciation, one of the largest ice ages, affecting the southern continents. The southern continents refer to the so-called Gondwana, an ancient supercontinent that included Antarctica, Australia, South America, India and Africa.

The most recent glaciation refers to the period in which we live. The Quaternary period of the Cenozoic era began about 2.5 million years ago, when the glaciers of the Northern Hemisphere reached the sea. But the first signs of this glaciation date back 50 million years ago in Antarctica.

The structure of each ice age is periodic: there are relatively short warm epochs, and there are longer periods of icing. Naturally, cold periods are not the result of glaciation alone. Glaciation is the most obvious consequence of cold periods. However, there are quite long intervals that are very cold, despite the absence of glaciations. Today, examples of such regions are Alaska or Siberia, where it is very cold in winter, but there is no glaciation, because there is not enough rainfall to provide enough water for the formation of glaciers.

Discovery of ice ages

The fact that there are ice ages on Earth has been known to us since the middle of the 19th century. Among the many names associated with the discovery of this phenomenon, the first is usually the name of Louis Agassiz, a Swiss geologist who lived in the middle of the 19th century. He studied the glaciers of the Alps and realized that they were once much more extensive than they are today. It wasn't just him who noticed. In particular, Jean de Charpentier, another Swiss, also noted this fact.

It is not surprising that these discoveries were made mainly in Switzerland, since there are still glaciers in the Alps, although they are melting quite quickly. It is easy to see that once the glaciers were much larger - just look at the Swiss landscape, the troughs (glacial valleys) and so on. However, it was Agassiz who first put forward this theory in 1840, publishing it in the book "Étude sur les glaciers", and later, in 1844, he developed this idea in the book "Système glaciare". Despite initial skepticism, over time, people began to realize that this was indeed true.

With the advent of geological mapping, especially in Northern Europe, it became clear that earlier glaciers had a huge scale. Then there were extensive discussions about how this information relates to the Flood, because there was a conflict between geological evidence and biblical teachings. Initially, glacial deposits were called deluvial because they were considered evidence of the Flood. Only later it became known that such an explanation is not suitable: these deposits were evidence of a cold climate and extensive glaciation. By the beginning of the 20th century, it became clear that there were many glaciations, and not just one, and from that moment this area of ​​​​science began to develop.

Ice Age Research

Known geological evidence of ice ages. The main evidence for glaciations comes from the characteristic deposits formed by glaciers. They are preserved in the geological section in the form of thick ordered layers of special deposits (sediments) - diamicton. These are simply glacial accumulations, but they include not only deposits of a glacier, but also deposits of melt water formed by its flows, glacial lakes or glaciers moving into the sea.

There are several forms of glacial lakes. Their main difference is that they are a water body enclosed by ice. For example, if we have a glacier that rises into a river valley, then it blocks the valley like a cork in a bottle. Naturally, when ice blocks a valley, the river will still flow and the water level will rise until it overflows. Thus, a glacial lake is formed through direct contact with ice. There are certain deposits that are contained in such lakes that we can identify.

Due to the way glaciers melt, which depends on seasonal changes in temperature, there is an annual melting of ice. This leads to an annual increase in minor sediments falling from under the ice into the lake. If we then look into the lake, we see stratification (rhythmic layered sediments) there, which is also known by the Swedish name "varves" ( varve), which means "annual accumulation". So we can actually see annual layering in glacial lakes. We can even count these varves and find out how long this lake has existed. In general, with the help of this material, we can get a lot of information.

In Antarctica, we can see huge ice shelves that come off the land into the sea. And of course, ice is buoyant, so it floats on water. As it swims, it carries pebbles and minor sediments with it. Due to the thermal action of the water, the ice melts and sheds this material. This leads to the formation of the process of the so-called rafting of rocks that go into the ocean. When we see fossil deposits from this period, we can find out where the glacier was, how far it extended, and so on.

Causes of glaciation

Researchers believe that ice ages occur because the Earth's climate depends on the uneven heating of its surface by the Sun. So, for example, the equatorial regions, where the Sun is almost vertically overhead, are the warmest zones, and the polar regions, where it is at a large angle to the surface, are the coldest. This means that the difference in heating of different parts of the Earth's surface controls the ocean-atmospheric machine, which is constantly trying to transfer heat from the equatorial regions to the poles.

If the Earth were an ordinary sphere, this transfer would be very efficient, and the contrast between the equator and the poles would be very small. So it was in the past. But since there are now continents, they get in the way of this circulation, and the structure of its flows becomes very complex. Simple currents are restrained and altered, in large part by mountains, leading to the circulation patterns we see today that drive the trade winds and ocean currents. For example, one of the theories about why the ice age began 2.5 million years ago links this phenomenon with the emergence of the Himalayan mountains. The Himalayas are still growing very fast and it turns out that the existence of these mountains in a very warm part of the Earth governs things like the monsoon system. The beginning of the Quaternary Ice Age is also associated with the closing of the Isthmus of Panama, which connects the north and south of America, which prevented the transfer of heat from the equatorial Pacific to the Atlantic.

If the position of the continents relative to each other and relative to the equator allowed the circulation to work efficiently, then it would be warm at the poles, and relatively warm conditions would persist throughout the earth's surface. The amount of heat received by the Earth would be constant and vary only slightly. But since our continents create serious barriers to circulation between north and south, we have pronounced climatic zones. This means that the poles are relatively cold while the equatorial regions are warm. When things are happening as they are now, the Earth can change with variations in the amount of solar heat it receives.

These variations are almost completely constant. The reason for this is that over time the earth's axis changes, as does the earth's orbit. Given this complex climatic zoning, orbital change could contribute to long-term changes in climate, resulting in climate wobble. Because of this, we have not continuous icing, but periods of icing, interrupted by warm periods. This happens under the influence of orbital changes. The latest orbital changes are seen as three separate phenomena: one 20,000 years long, the second 40,000 years long, and the third 100,000 years long.

This led to deviations in the pattern of cyclic climate change during the Ice Age. The icing most likely occurred during this cyclic period of 100,000 years. The last interglacial epoch, which was as warm as the current one, lasted about 125,000 years, and then came a long ice epoch, which took about 100,000 years. We are now living in another interglacial era. This period will not last forever, so another ice age awaits us in the future.

Why do ice ages end?

Orbital changes change the climate, and it turns out that ice ages are characterized by alternating cold periods, which can last up to 100,000 years, and warm periods. We call them the glacial (glacial) and interglacial (interglacial) epochs. An interglacial era is usually characterized by conditions similar to what we see today: high sea levels, limited areas of icing, and so on. Naturally, even now there are glaciations in Antarctica, Greenland and other similar places. But in general, the climatic conditions are relatively warm. This is the essence of interglacial: high sea level, warm temperature conditions and, in general, a fairly even climate.

But during the ice age, the average annual temperature changes significantly, the vegetative belts are forced to shift north or south, depending on the hemisphere. Regions like Moscow or Cambridge become uninhabited, at least in winter. Although they may be habitable in summer due to the strong contrast between seasons. But what is actually happening is that the cold zones are expanding substantially, the average annual temperature is dropping, and the overall climate is getting very cold. While the largest glacial events are relatively limited in time (perhaps around 10,000 years), the entire long cold period can last 100,000 years or more. This is what the glacial-interglacial cycle looks like.

Due to the length of each period, it is difficult to say when we will exit the current era. This is due to plate tectonics, the location of the continents on the surface of the Earth. Currently, the North Pole and South Pole are isolated, with Antarctica at the South Pole and the Arctic Ocean to the north. Because of this, there is a problem with heat circulation. As long as the location of the continents does not change, this ice age will continue. In line with long-term tectonic changes, it can be assumed that it will take another 50 million years in the future until significant changes occur that allow the Earth to emerge from the ice age.

Geological implications

Of course, the main consequence of the Ice Age is huge ice sheets. Where does water come from? Of course, from the oceans. What happens during ice ages? Glaciers form as a result of precipitation on land. Due to the fact that the water does not return to the ocean, the sea level falls. During the most severe glaciations, sea levels can drop by more than a hundred meters.

This frees up huge sections of the continental shelf that are flooded today. This will mean, for example, that one day it will be possible to walk from Britain to France, from New Guinea to Southeast Asia. One of the most critical places is the Bering Strait, which links Alaska with Eastern Siberia. It is quite small, about 40 meters, so if the sea level drops to a hundred meters, then this area will become land. This is also important because plants and animals will be able to migrate through these places and get into regions where they cannot go today. Thus, the colonization of North America depends on the so-called Beringia.

Animals and the Ice Age

It is important to remember that we ourselves are the "products" of the ice age: we evolved during it, so we can survive it. However, it is not a matter of individual individuals - it is a matter of the entire population. The problem today is that there are too many of us and our activities have significantly changed the natural conditions. Under natural conditions, many of the animals and plants that we see today have a long history and survive the Ice Age well, although there are some that evolved slightly. They migrate and adapt. There are zones in which animals and plants survived the Ice Age. These so-called refugiums were located further north or south from their present distribution.

But as a result of human activity, some species died or became extinct. This has happened on every continent, with the possible exception of Africa. A huge number of large vertebrates, namely mammals, as well as marsupials in Australia, were exterminated by man. This was caused either directly by our activities, such as hunting, or indirectly by the destruction of their habitat. Animals living in northern latitudes today lived in the Mediterranean in the past. We have destroyed this region so much that it will most likely be very difficult for these animals and plants to colonize it again.

Consequences of global warming

Under normal conditions, by geological standards, we would soon enough return to the Ice Age. But because of global warming, which is a consequence of human activity, we are postponing it. We will not be able to completely prevent it, since the causes that caused it in the past still exist today. Human activity, an unforeseen element of nature, affects atmospheric warming, which may have already caused a delay in the next glacial.

Today, climate change is a very relevant and exciting issue. If the Greenland Ice Sheet melts, sea levels will rise by six meters. In the past, during the previous interglacial epoch, which was about 125,000 years ago, the Greenland Ice Sheet melted profusely, and sea levels were 4–6 meters higher than today. It's certainly not the end of the world, but it's not time complexity either. After all, the Earth has recovered from catastrophes before, it will be able to survive this one.

The long-term outlook for the planet is not bad, but for humans, that's a different matter. The more research we do, the better we understand how the Earth is changing and where it leads, the better we understand the planet we live on. This is important because people are finally starting to think about changing sea levels, global warming and the impact of all these things on agriculture and the population. Much of this has to do with the study of ice ages. Through these studies, we will learn the mechanisms of glaciation, and we can use this knowledge proactively in an attempt to mitigate some of the changes that we ourselves are causing. This is one of the main results and one of the goals of research on ice ages.

This is a translation of an article from our English edition of Serious Science. You can read the original version of the text here.

Great Quaternary glaciation

Geologists have divided the entire geological history of the Earth, which has been going on for several billion years, into eras and periods. The last of these, which continues to this day, is the Quaternary period. It began almost a million years ago and was marked by the extensive distribution of glaciers on the globe - the Great Ice Age of the Earth.

Thick ice caps covered the northern part of the North American continent, a significant part of Europe, and possibly Siberia as well (Fig. 10). In the southern hemisphere, under the ice, as now, was the entire Antarctic continent. There was more ice on it - the surface of the ice sheet rose 300 m above its current level. However, as before, Antarctica was surrounded on all sides by a deep ocean, and the ice could not move north. The sea prevented the growth of the Antarctic giant, and the continental glaciers of the northern hemisphere were spreading to the south, turning flowering spaces into an icy desert.

Man is the same age as the Great Quaternary glaciation of the Earth. His first ancestors - ape people - appeared at the beginning of the Quaternary period. Therefore, some geologists, in particular the Russian geologist A.P. Pavlov, proposed calling the Quaternary period Anthropogenic (in Greek, "anthropos" - a man). Several hundred thousand years passed before man took on his modern appearance. The onset of glaciers worsened the climate and living conditions of ancient people who had to adapt to the harsh nature around them. People had to lead a settled way of life, build dwellings, invent clothes, use fire.

Having reached the greatest development 250 thousand years ago, the Quaternary glaciers began to gradually shrink. The Ice Age was not unified throughout the Quaternary. Many scientists believe that during this time the glaciers completely disappeared at least three times, giving way to interglacial epochs, when the climate was warmer than the present. However, these warm epochs were replaced by cooling periods, and glaciers spread again. Now we live, apparently, at the end of the fourth stage of the Quaternary glaciation. After the liberation of Europe and America from under the ice, these continents began to rise - this is how the earth's crust reacted to the disappearance of the glacial load that had been pressing on it for many thousands of years.

The glaciers “left”, and after them, vegetation, animals spread to the north, and, finally, people settled. Since the glaciers retreated unevenly in different places, humanity also settled unevenly.

Retreating, the glaciers left behind smoothed rocks - "ram's foreheads" and boulders covered with hatching. This hatching is formed from the movement of ice on the surface of the rocks. It can be used to determine in which direction the glacier moved. The classic area of ​​manifestation of these traits is Finland. The glacier retreated from here quite recently, less than ten thousand years ago. Modern Finland is the land of countless lakes lying in shallow depressions, between which low “curly” rocks rise (Fig. 11). Here everything reminds of the former greatness of glaciers, their movement and huge destructive work. Close your eyes and you immediately imagine how slowly, year after year, century after century, a powerful glacier creeps here, how it plows its bed, breaks off huge blocks of granite and carries them south, towards the Russian Plain. It is no coincidence that it was while in Finland that P. A. Kropotkin thought about the problems of glaciation, collected a lot of disparate facts and managed to lay the foundations for the theory of the ice age on Earth.

There are similar corners at the other "end" of the Earth - in Antarctica; not far from the village of Mirny, for example, is the "oasis" of Banger - a free ice-free land area of ​​​​600 km2. When you fly over it, small chaotic hills rise under the wing of the aircraft, and between them bizarrely shaped lakes snake. Everything is the same as in Finland and ... it doesn’t look like it at all, because in Banger’s “oasis” there is no main thing - life. Not a single tree, not a single blade of grass - only lichens on the rocks, and algae in the lakes. Probably, all the territories recently freed from under the ice were once the same as this "oasis". The glacier left the surface of the “oasis” of Bunger only a few thousand years ago.

The Quaternary glacier also extended to the territory of the Russian Plain. Here, the movement of ice slowed down, it began to melt more and more, and somewhere in the place of the modern Dnieper and Don, powerful streams of melt water flowed from under the edge of the glacier. Here passed the border of its maximum distribution. Later, on the Russian Plain, many remnants of the spread of glaciers were found, and above all, large boulders, like those that were often encountered on the path of Russian epic heroes. In thought, the heroes of old fairy tales and epics stopped at such a boulder before choosing their long road: right, left or go straight. These boulders have long stirred the imagination of people who could not understand how such colossi ended up on a plain among dense forests or endless meadows. They came up with various fabulous reasons, and there was a “global flood”, during which the sea allegedly brought these stone blocks. But everything was explained much more simply - a huge flow of ice with a thickness of several hundred meters cost nothing to “move” these boulders a thousand kilometers.

Almost halfway between Leningrad and Moscow there is a picturesque hilly-lake region - the Valdai Upland. Here, among the dense coniferous forests and plowed fields, the waters of many lakes splash: Valdai, Seliger, Uzhino and others. The shores of these lakes are indented, they have many islands, densely overgrown with forests. It was here that the border of the last distribution of glaciers on the Russian Plain passed. It was the glaciers that left behind strange shapeless hills, the depressions between them were filled with their meltwater, and subsequently the plants had to work hard to create good living conditions for themselves.

About the causes of the great glaciations

So, glaciers on Earth were not always. Even in Antarctica, coal has been found - a sure sign that there was a warm and humid climate with rich vegetation. At the same time, geological data testify that the great glaciations were repeated on Earth repeatedly every 180-200 million years. The most characteristic traces of glaciation on Earth are special rocks - tillites, that is, the petrified remains of ancient glacial moraines, consisting of a clay mass with the inclusion of large and small hatched boulders. Individual thicknesses of tillites can reach tens and even hundreds of meters.

The causes of such major climate changes and the occurrence of the great glaciations of the Earth are still a mystery. Many hypotheses have been put forward, but none of them can yet claim the role of a scientific theory. Many scientists have been looking for the cause of the cooling outside the Earth, putting forward astronomical hypotheses. One of the hypotheses is that glaciation arose when, due to fluctuations in the distance between the Earth and the Sun, the amount of solar heat received by the Earth changed. This distance depends on the nature of the Earth's movement in its orbit around the Sun. It was assumed that glaciation set in when winter fell on aphelion, i.e., the point of the orbit most distant from the Sun, at the maximum elongation of the earth's orbit.

However, recent studies by astronomers have shown that a change in the amount of solar radiation hitting the Earth alone is not enough to cause an ice age, although such a change should have its consequences.

The development of glaciation is also associated with fluctuations in the activity of the Sun itself. Heliophysicists have long found out that dark spots, flares, prominences appear periodically on the Sun, and even learned how to predict their occurrence. It turned out that solar activity changes periodically; there are periods of different duration: 2-3, 5-6, 11, 22 and about a hundred years. It may happen that the climaxes of several periods of different durations will coincide, and solar activity will be especially great. So, for example, it was in 1957 - just in the period of the International Geophysical Year. But it may be the other way around - several periods of reduced solar activity will coincide. This can cause the development of glaciation. As we will see later, such changes in solar activity are reflected in the activity of glaciers, but they are unlikely to cause a great glaciation of the Earth.

Another group of astronomical hypotheses can be called cosmic. These are assumptions that the cooling of the Earth is influenced by various parts of the Universe that the Earth passes through, moving in space along with the entire Galaxy. Some believe that the cooling occurs when the Earth "floats" parts of world space filled with gas. Others are when it passes through clouds of cosmic dust. Still others argue that "space winter" on Earth happens when the globe is in apogalactia - the point furthest from that part of our Galaxy where the most stars are located. At the present stage of the development of science, it is not possible to support all these hypotheses with facts.

The most fruitful hypotheses are those in which the cause of climate change is assumed to be on the Earth itself. According to many researchers, the cooling that causes glaciation may occur as a result of changes in the location of land and sea, under the influence of the movement of the continents, due to a change in the direction of sea currents (for example, the Gulf Stream was previously deflected by a land ledge that stretched from Newfoundland to the Green Islands). cape). There is a widely known hypothesis according to which, during the epochs of mountain building on Earth, large masses of continents that rose up fell into higher layers of the atmosphere, cooled down and became places for the birth of glaciers. According to this hypothesis, epochs of glaciation are associated with epochs of mountain building, moreover, they are conditioned by them.

The climate can change significantly as a result of a change in the tilt of the earth's axis and the movement of the poles, as well as due to fluctuations in the composition of the atmosphere: there is more volcanic dust or less carbon dioxide in the atmosphere, and the Earth becomes much colder. Recently, scientists have begun to associate the appearance and development of glaciation on Earth with the restructuring of the atmospheric circulation. When, under the same climatic background of the globe, too much precipitation falls into individual mountainous regions, then glaciation occurs there.

A few years ago, American geologists Ewing and Donn put forward a new hypothesis. They suggested that the Arctic Ocean, now covered in ice, thawed at times. In this case, increased evaporation occurred from the surface of the Arctic sea, which was free from ice, and humid air flows were directed towards the polar regions of America and Eurasia. Here, above the cold surface of the earth, abundant snow fell from moist air masses, which did not have time to melt over the summer. Thus, ice sheets appeared on the continents. Spreading, they descended to the north, surrounding the Arctic Sea with an ice ring. As a result of the transformation of part of the moisture into ice, the level of the world's oceans dropped by 90 m, the warm Atlantic Ocean ceased to communicate with the Arctic Ocean, and it gradually froze. Evaporation from its surface ceased, less snow began to fall on the continents, and the nutrition of glaciers deteriorated. Then the ice sheets began to thaw, decrease in size, and the level of the world's oceans rose. Again, the Arctic Ocean began to communicate with the Atlantic Ocean, its waters warmed up, and the ice cover on its surface began to gradually disappear. The cycle of development of glaciation began from the beginning.

This hypothesis explains some facts, in particular, several advances of glaciers during the Quaternary period, but it also does not answer the main question: what is the cause of the Earth's glaciations.

So, we still do not know the causes of the great glaciations of the Earth. With a sufficient degree of certainty, we can only talk about the last glaciation. Usually glaciers shrink unevenly. There are periods when their retreat is long delayed, and sometimes they advance rapidly. It is noted that such oscillations of glaciers occur periodically. The longest period of alternation of retreats and advances lasts for many centuries.

Some scientists believe that climate change on Earth, which is associated with the development of glaciers, depends on the relative position of the Earth, the Sun and the Moon. When these three celestial bodies are in the same plane and on the same straight line, the tides on Earth increase sharply, the circulation of water in the oceans and the movement of air masses in the atmosphere change. Ultimately, there is a slight increase in rainfall and a decrease in temperature around the globe, which leads to the growth of glaciers. Such an increase in the moistening of the globe is repeated every 1800-1900 years. The last two such periods were in the 4th c. BC e. and the first half of the fifteenth century. n. e. On the contrary, in the interval between these two maxima, the conditions for the development of glaciers should be less favorable.

On the same basis, it can be assumed that in our modern era, glaciers must retreat. Let's see how glaciers actually behaved in the last millennium.

Development of glaciation in the last millennium

In the X century. Icelanders and Normans, sailing along the northern seas, discovered the southern tip of an immensely large island, the shores of which were overgrown with thick grass and tall shrubs. This impressed the sailors so much that they named the island Greenland, which means "Green Country".

Why, then, was the most icy island on the globe so flourishing at that time? Obviously, the peculiarities of the then climate led to the retreat of glaciers, the melting of sea ice in the northern seas. The Normans were able to pass freely from Europe to Greenland on small ships. Settlements were founded on the coast of the island, but they did not last long. The glaciers began to advance again, the "ice cover" of the northern seas increased, and attempts to reach Greenland in subsequent centuries usually ended in failure.

By the end of the first millennium of our era, the mountain glaciers in the Alps, the Caucasus, Scandinavia and Iceland also strongly receded. Some passes, previously occupied by glaciers, became passable. The lands freed from glaciers began to be cultivated. Prof. G. K. Tushinsky recently examined the ruins of the settlements of the Alans (ancestors of the Ossetians) in the Western Caucasus. It turned out that many buildings dating back to the 10th century are located in places that are now completely unsuitable for habitation due to frequent and destructive avalanches. This means that a thousand years ago, not only glaciers "moved" closer to the mountain ridges, but avalanches did not descend here either. However, in the future, winters became more severe and snowy, avalanches began to fall closer to residential buildings. The Alans had to build special avalanche dams, their remnants can still be seen today. In the end, it turned out to be impossible to live in the former villages, and the highlanders had to settle down in the valleys.

The beginning of the 15th century was approaching. Living conditions became more and more severe, and our ancestors, who did not understand the reasons for such a cold snap, were very worried about their future. Increasingly, records of cold and difficult years appear in the annals. In the Tver Chronicle one can read: “In the summer of 6916 (1408) ... but then the winter was hard and very cold, snowy too much”, or “In the summer of 6920 (1412) the winter was very snowy, and therefore in the spring it was the water is great and strong." The Novgorod Chronicle says: “In the summer of 7031 (1523) ... the same spring, on Trinity Day, a large cloud of snow fell, and snow lay on the ground for 4 days, but the stomach, horses and cows froze a lot, and the birds died in the forest ". In Greenland, due to the onset of cooling by the middle of the XIV century. ceased to be engaged in cattle breeding and agriculture; the connection between Scandinavia and Greenland was broken due to the abundance of sea ice in the northern seas. In some years, the Baltic and even the Adriatic Sea froze. From the 15th to the 17th century mountain glaciers advanced in the Alps and the Caucasus.

The last great advance of glaciers dates back to the middle of the last century. In many mountainous countries they have advanced quite far. Traveling in the Caucasus, G. Abikh in 1849 discovered traces of the rapid advance of one of the Elbrus glaciers. This glacier has invaded a pine forest. Many trees were broken and lay on the surface of the ice or stuck through the body of the glacier, and their crowns were completely green. Documents have been preserved that tell about frequent ice landslides from Kazbek in the second half of the 19th century. Sometimes, because of these landslides, it was impossible to drive along the Georgian Military Highway. Traces of rapid advances of glaciers at this time are known in almost all inhabited mountainous countries: in the Alps, in the west of North America, in Altai, in Central Asia, as well as in the Soviet Arctic and in Greenland.

With the advent of the 20th century, global warming begins almost everywhere. It is associated with a gradual increase in solar activity. The last maximum solar activity was in 1957-1958. During these years, a large number of sunspots and extremely strong solar flares were observed. In the middle of our century, the maxima of three cycles of solar activity coincided - eleven-year, secular and supersecular. It should not be thought that the increased activity of the Sun leads to an increase in heat on the Earth. No, the so-called solar constant, that is, the value showing how much heat comes to each section of the upper boundary of the atmosphere, remains unchanged. But the flow of charged particles from the Sun to the Earth and the overall impact of the Sun on our planet is increasing, and the intensity of atmospheric circulation throughout the Earth is increasing. Streams of warm and humid air from tropical latitudes rush to the polar regions. And this leads to a rather sharp warming. In the polar regions, it warms up sharply, and then it gets warmer throughout the Earth.

In the 20-30s of our century, the average annual air temperature in the Arctic increased by 2-4°. The sea ice boundary has moved north. The Northern Sea Route has become more passable for ships, the period of polar navigation has lengthened. The glaciers of Franz Josef Land, Novaya Zemlya and other Arctic islands have been retreating rapidly over the past 30 years. It was during these years that one of the last Arctic ice shelves, located on Ellesmere Land, collapsed. In our time, glaciers are retreating in the vast majority of mountainous countries.

A few years ago, almost nothing could be said about the nature of temperature changes in the Antarctic: there were too few meteorological stations and there were almost no expeditionary studies. But after summing up the results of the International Geophysical Year, it became clear that in the Antarctic, as in the Arctic, in the first half of the 20th century. the air temperature rose. There are some interesting pieces of evidence for this.

The oldest Antarctic station is Little America on the Ross Ice Shelf. Here, from 1911 to 1957, the average annual temperature increased by more than 3°. On Queen Mary Land (in the area of ​​modern Soviet research) for the period from 1912 (when the Australian expedition led by D. Mawson conducted research here) to 1959, the average annual temperature increased by 3.6°C.

We have already said that at a depth of 15-20 m in the thickness of snow and firn, the temperature should correspond to the average annual temperature. However, in reality, at some inland stations, the temperature at these depths in the wells turned out to be 1.3-1.8° lower than the average annual temperatures over several years. Interestingly, the temperature continued to drop as one went deeper into these boreholes (up to a depth of 170 m), while usually the temperature of the rocks becomes higher with increasing depth. This unusual temperature drop in the ice sheet is a reflection of the colder climate of those years when snow was deposited, now at a depth of several tens of meters. Finally, it is very indicative that the extreme boundary of the distribution of icebergs in the Southern Ocean is now located 10-15 ° south of latitude compared to 1888-1897.

It would seem that such a significant increase in temperature over several decades should lead to the retreat of the Antarctic glaciers. But this is where the "difficulties of Antarctica" begin. They are partly due to the fact that we still know too little about it, and partly due to the great originality of the ice colossus, which is completely different from the mountain and arctic glaciers we are used to. Let's try to figure out what is happening now in Antarctica, and for this we will get to know it better.