Over the past million years, an ice age has occurred on Earth approximately every 100,000 years. This cycle actually exists, and different groups of scientists at different times tried to find the reason for its existence. True, there is no prevailing point of view on this issue yet.
More than a million years ago, the cycle was different. The ice age was replaced by climate warming about once every 40 thousand years. But then the frequency of the glaciers' advance changed from 40 thousand years to 100 thousand. Why did this happen?
Experts from Cardiff University have offered their own explanation for this change. The results of the scientists' work were published in the authoritative publication Geology. According to experts, the main reason for the change in the periodicity of the onset of ice ages is the oceans, or rather, their ability to absorb carbon dioxide from the atmosphere.
By studying the sediments that make up the ocean floor, the team found that CO2 concentrations vary from layer to layer of sediment, just over 100,000 years. It is likely, scientists say, that excess carbon dioxide was extracted from the atmosphere by the ocean's surface, with the further binding of this gas. As a result, the average annual temperature gradually decreases, and the next ice age begins. And it so happened that the duration of the ice age more than a million years ago increased, and the cycle "heat-cold" became longer.
“It is likely that the oceans absorb and release carbon dioxide, and when the ice gets larger, the oceans absorb more carbon dioxide from the atmosphere, making the planet colder. When ice is scarce, the oceans release carbon dioxide, so the climate gets warmer,”says Professor Carrie Lear. “By studying the concentration of carbon dioxide in the remains of tiny creatures (here we mean sedimentary rocks, - editor's note), we learned that during periods when the glacier area increased, the oceans absorbed more carbon dioxide, so it can be assumed that there is less of it in the atmosphere."
Algae are said to have played a major role in CO2 uptake, as carbon dioxide is an essential component of photosynthesis.
Carbon dioxide enters the atmosphere from the ocean as a result of upwelling. Upwelling is the process by which deep ocean waters rise to the surface. It is most often observed at the western borders of continents, where it moves colder, nutrient-rich waters from the depths of the ocean to the surface, replacing warmer, nutrient-poor surface waters. It can also be found in almost any area of the world's oceans.
A layer of ice on the surface of the water prevents carbon dioxide from entering the atmosphere, so if much of the ocean freezes over, it prolongs the ice age. “If we believe that the oceans emit and absorb carbon dioxide, then we must understand that a large amount of ice prevents this process. It's like a lid on the surface of the ocean,”says Professor Liar.
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With an increase in the area of glaciers on the ice surface, not only does the concentration of "warming" CO2 decrease, but the albedo of those regions covered by ice also increases. As a result, the planet receives less energy, which means it cools down even faster.
Now there is an interglacial, warm period on Earth. The last ice age ended about 11,000 years ago. Since then, the average annual temperature and sea level have steadily increased, and the amount of ice on the surface of the oceans has been decreasing. As a result, scientists believe that large amounts of CO2 are released into the atmosphere. Plus, humans also produce carbon dioxide, and in huge quantities.
All this led to the fact that in September the concentration of carbon dioxide in the Earth's atmosphere increased to 400 parts per million. This figure has increased from 280 to 400 parts per million in just 200 years of industrial development. Most likely, CO2 in the atmosphere will not decrease in the foreseeable future. All this should lead to an increase in the average annual temperature on Earth by about + 5 ° C in the next thousand years.
The Climate Department at the Potsdam Observatory recently built a model for the Earth's climate, taking into account the global carbon cycle. As the model showed, even with minimal levels of carbon dioxide emissions into the atmosphere, the ice sheet of the Northern Hemisphere will not be able to increase. This means that the onset of the next ice age may move forward by at least 50-100 thousand years. So the next change in the cycle "glaciers-warming" awaits us ahead, this time a person is responsible for it.
