Experts from Cardiff University have offered an explanation for why our planet enters and exits an ice age every 100,000 years. This mysterious phenomenon, called the "100,000 year problem," has been occurring regularly over the past million years, causing giant ice caps to cover North America, Europe and Asia. Until now, scientists had no idea how to explain this phenomenon.
The glaciation of our planet, as a rule, occurred at intervals of 40,000 years, which suited scientists, since the earth's seasons change in a predictable way: during these intervals, the summers are colder. However, about a million years ago, there was a "mid-Pleistocene transition", during which the intervals of the ice age changed from 40,000 to 100,000 years.
A new study, published recently in the journal Geology, showed that the oceans may be responsible for this change, or rather the process of sucking carbon dioxide from the atmosphere into them. By studying the chemical composition of tiny fossils on the ocean floor, scientists have found that more carbon dioxide accumulated in the depths of the ocean during the ice age than usual, and this happened at intervals of 100,000 years.
Consequently, at the same time, additional carbon dioxide was flowing from the atmosphere into the oceans, lowering the temperature on Earth and allowing huge slabs of ice to absorb the northern hemisphere.
The study's lead author, Professor Carrie Lear of the School of Earth and Ocean Sciences, says: “You can imagine the oceans breathing in and out carbon dioxide, so when the ice sheets are larger, the oceans breathe in carbon dioxide from the atmosphere, making the planet colder. When the plates are smaller, the oceans breathe out carbon dioxide, which gets back into the atmosphere and warms the planet."
"By studying the fossils of tiny creatures at the bottom of the ocean, we showed that when sheets of ice came in and out every 100,000 years, the oceans breathed in more carbon dioxide during colder periods and less remained in the atmosphere."
Algae play a key role in removing carbon dioxide from the atmosphere, as this gas is an essential component of photosynthesis.
Carbon dioxide returns to the atmosphere when deep ocean waters rise to the surface during upwelling, but if there is a lot of ice in the sea, it prevents carbon dioxide from escaping, ice plates get larger and the ice age prolongs. Large amounts of ice cover the ocean.
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Currently, the earth's climate is in the golden mean between ice ages. The last ice age ended about 11,000 years ago. Since then, temperatures and sea levels have risen, and the ice caps have retreated back to the poles. In addition to natural cycles, man-made carbon emissions also contribute to climate warming.
ILYA KHEL
