Why did Antarctica become covered with glaciers? Greenland is covered in ice due to a lack of carbon dioxide - scientists Climate, glaciers and the local population

Some still prefer not to believe in global warming, despite the fact that scientists have already predicted the timing of the increase in the planet’s temperature, the maximum temperatures that residents of all regions will have to face, and even catastrophic processes of extinction and real escape flora and fauna.

Scientists themselves were led to believe in the ability of global warming to lead to rapid processes by satellite images of the melting of huge Antarctic glaciers - in 2002, the Larsen Ice Shelf the size of a small European state disappeared from monitor screens within a month. Until recently, scientists believed that the melting of such quantities of ice would take many years, if not decades.

Having dealt with the melting of ice and predicted the imminent disappearance of the Arctic ice cap, glaciologists still do not know the reasons for the reverse process - for example, how the second largest ice sheet on Earth, Greenland, was formed. It still surprises scientists to this day - at the same latitudes, neither in Canada nor in the Siberian expanses, there is no year-round ice cover.

Researchers led by Dan Lunt from the University of Bristol have established the most likely reason for the formation of this huge piece of ice three million years ago, although they still do not draw final conclusions.

It has long been known that the melting of all the ice in Greenland would be enough to raise the level of the world's seas by 6.5 meters. For many states, especially small and coastal ones, such a rise will be very unpleasant, if not catastrophic. However, such a threat scares ordinary citizens little, since so far none of the scientists undertakes to say exactly when and how quickly the Greenland ice will melt.

If the process of its melting lasts for centuries, this can already be considered an environmental disaster, but many researchers are much more pessimistic. Large-scale melting of the Greenland ice sheet has already begun, with meltwater seeping through cracks in the ice shell, serves as a kind of lubricant, facilitating the sliding of broken ice blocks into the ocean. If this self-accelerating melting process continues to increase its pace, then we will have to say goodbye to the Greenland ice in just a few decades.

The remaining uncertainty about the mechanisms of melting and formation of ice, the increase in the planet's temperature and the volume of ice reserves in Greenland allows some to hope for a slight rise of water, just a few decimeters, by the end of this century. However, it is unlikely that anyone will argue that it is better to prepare for a sudden increase in water levels, if it happens, than to rely on optimistic forecasts and sit with arms folded.

IN work, published in the latest issue of Nature, scientists from the University of Bristol showed exactly what force has held Greenland's ice until now and how dangerous a further increase in the concentration of carbon dioxide in the atmosphere is.

Lunt wanted to find out what exactly led to the formation of the Greenland shield. This happened three million years ago. The sedimentary layers of that era, now covered by the waters washing Greenland, contain many fragmented rocks that were brought here by icebergs breaking off from the Greenland coast. Until this point, Greenland was covered with green meadows and forests.

Why did Greenland suddenly become covered in ice? Scientists have several hypotheses on this matter - firstly, this could happen due to the changed regime of global circulation of ocean waters, which still bring heat to Europe. In addition, the icing of this area of the earth's surface can also be associated with small fluctuations in the earth's orbit. Tectonic processes that raised the surface of the island could also lead to the appearance of an ice shell.

All these hypotheses have a certain basis, but Dunt still seemed doubtful about the scale of the consequences of the manifestation of these forces.

In his opinion, only a sharp decrease in the level of atmospheric carbon dioxide to the level of the pre-industrial era of mankind could so radically change the appearance of Greenland.

He was able to prove this using computer modeling, which revealed the consequences of various scenarios for the formation of the Greenland ice sheet. It turned out that even a significant rise in the surface of the island above sea level is not capable of covering the entire island with ice.

Comparative increase in the Greenland ice sheet as a result of tectonic uplift of the Greenland Rocky Mountains and as a result of falling atmospheric carbon dioxide concentrations.//Dan Lunt, University of Bristol

As for the level of atmospheric CO 2, its concentration in the air before the Greenland glaciation was 400 parts per million by volume (ppm). In the pre-industrial era, this concentration was 280 ppm, although in recent centuries it has increased to 385 ppm.

As Lunt noted in interview LiveScience, its study only shows how sensitive the enormous Greenland ice sheet is to changes in atmospheric CO 2 concentrations.

However, it also cannot explain why Greenland is covered with ice, while the corresponding territories of Canada and Siberia are completely free of snow in the summer.

Perhaps the rocky mountains of Greenland are high enough for glaciers to form on them in the summer, and then spread throughout the island. Siberia and Canada are covered with ice only when the next deviation of the earth's orbit leads to the onset of a new ice age.

The most intriguing question remains unanswered: what exactly led to the sharp drop in atmospheric concentrations of carbon dioxide, and what level of CO 2 is normal for our planet.

28/08/2008

MOSCOW, August 28 - RIA Novosti. The main reason for the appearance of the glacier that now covers the entire territory of Greenland 3 million years ago was a drop in the concentration of carbon dioxide in the atmosphere, according to a paper published by British scientists on Thursday in the journal Nature.

According to experts, understanding the reasons for the formation of the Greenland glacier will help understand its possible response to future climate change.

The authors of the study, scientists from the universities of Bristol and Leeds, used computer modeling to test a number of hypotheses about the causes of the Greenland glacier and came to the conclusion that only an increase in carbon dioxide levels can explain the transformation of ice-free Greenland into the current ice-bound island.

According to one of the study's authors, Dr Dan Lunt from Bristol, about 3 million years ago the amount of rock debris in the sediments around Greenland increased. They could not appear until the mass appearance of icebergs, which “scraped” this rock from the surface of the island into the ocean.

"This suggests that significant amounts of ice only began to appear in Greenland 3 million years ago. Before then, Greenland was largely ice-free and possibly covered with grass and forests. In addition, the concentration of carbon dioxide was relatively high. Question , which we wanted to answer - why did Greenland get an ice sheet?" - says Lunt, whose words are quoted in a university statement.

There are several theories explaining the appearance of the Greenland glacier.

According to one of them, ice in Greenland appeared due to the appearance of the Isthmus of Panama, which connected South and North America 13-2.5 million years ago. The disappearance of the Panama Strait led to an increase in the difference in salinity between the Atlantic and Pacific oceans and an increase in humidity in the North Atlantic. As a result, the amount of snow falling in the Greenland region increased sharply, and glacier growth began.

Another theory links the emergence of Greenland ice to tectonic changes - the growth of the Rocky Mountains and the Himalayas, which led to changes in atmospheric circulation.

A number of researchers associate the appearance of the glacier with changes in ocean circulation, others with changes in the earth's orbit, and still others with natural changes in the concentration of greenhouse gases.

Using cutting-edge computer models of climate and glacier dynamics, Lunt and his colleagues decided to test which of these theories best corresponded to reality.

Although the results showed that climate change associated with changes in ocean circulation and tectonic uplift affected the Greenland ice sheet, and the amount of ice also depended on fluctuations in Earth's orbit, neither of these factors was strong enough to make a significant contribution to long-term growth of the Greenland glacier.

The study found that the main cause of the Greenland glaciation was a drop in atmospheric carbon dioxide levels to levels close to pre-industrial levels. Current levels of carbon dioxide concentrations are approaching levels when Greenland was mostly ice-free.

Dr Alan Haywood from the University of Leeds adds that the reasons for the rise in carbon dioxide levels in the atmosphere are still unclear.

"This is the million-dollar question that researchers will undoubtedly be looking to answer over the next few years," he says.

MOSCOW, August 28 - RIA Novosti. The main reason for the appearance of the glacier that now covers the entire territory of Greenland 3 million years ago was a drop in the concentration of carbon dioxide in the atmosphere, according to a paper published by British scientists on Thursday in the journal Nature.

According to experts, understanding the reasons for the formation of the Greenland glacier will help understand its possible response to future climate change.

There are several theories explaining the appearance of the Greenland glacier.

Another theory links the emergence of Greenland ice to tectonic changes - the growth of the Rocky Mountains and the Himalayas, which led to changes in atmospheric circulation.

Using cutting-edge computer models of climate and glacier dynamics, Lunt and his colleagues decided to test which of these theories best corresponded to reality.

Dr Alan Haywood from the University of Leeds adds that the reasons for the rise in carbon dioxide levels in the atmosphere are still unclear.

"This is the million-dollar question that researchers will undoubtedly be looking to answer over the next few years," he says.

The reason is that modern Antarctica is a continent covered with a layer of many kilometers - a change in the circulation of world waters near its shores.

Antarctica is known to have had temperate forests in the past that were teeming with life of all kinds. About 33 million years ago, the continent quickly cooled and became an icy desert.

A study conducted by scientists at the Rensselaer Polytechnic Institute, USA, says that the cause of this environmental disaster is the formation of the Antarctic circumpolar current around the continent.

Before this study, it was argued that this current formed after a cold snap, i.e. approximately 23-25 million years ago. It now turns out that it was the initial emergence of the Antarctic circumpolar current that marked the beginning of climate change. A connection has now been established between the near-surface circumpolar current and the onset of a cooling period in Antarctica. The appearance of the circumpolar current, which is also called the Western Winds Current, formed the modern 4-layer structure of ocean waters.

Ocean temperature and planetary air temperature are interconnected; the higher the water temperature, the higher the average air temperature. Global ocean currents determine the difference in temperature between equatorial and polar waters.

In the period before the appearance of the circumpolar current, the difference in water temperature at the equator and off the coast of Antarctica was half as much as at present. But now this girdling current prevents the warm water of the South Atlantic Current from penetrating into the Antarctic continent, “pushing” it back into the Atlantic Ocean.

Global climate change in the Antarctic region occurred when the Drake Passage emerged between Antarctica and South America, and the Tasman Strait between Antarctica and Australia sharply expanded. In ancient times they made up one continent. The formation of a belt around Antarctica gave rise to a circumpolar current that cooled the continent.

In a new study, scientists have identified a more objective source of information about the temperature of those times. This source in the American study was oxygen isotopes with atomic weights 16 and 18. In the remains of ancient organisms, the content of heavy oxygen (isotope 18) varies depending on the temperature of the water in which they lived.

Tracing the isotope 18 of oxygen and magnesium and calcium in fossils from Antarctica and in samples from the northern regions of the Atlantic and Pacific ocean floors showed that temperatures dropped 2-3 degrees after the current appeared.

Reconstructing past climate conditions will allow scientists to study modern climate changes.

Why did Antarctica become covered with glaciers? Greenland is covered in ice due to a lack of carbon dioxide - scientists Climate, glaciers and the local population

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