Washington, .- A slowing of the circulation of water in the oceans around Antarctica drastically altered the intensity of the glacial epochs and doubled its duration throughout the world after the transition of the mid-Pleistocene, according to a study published today by the Science magazine.
In the last few million years, the natural cycle of Earth’s climate was dominated by the ebb and flow of tides during the glaciations and the periods between them, recalls the analysis of the American Association for the Advancement of Science.
Until now, it was thought that these cycles had to do with the orbit of the planet around the sun.
The variation in solar radiation that reaches the Earth depending on where the star is in its orbit around the sun has an influence on the Earth’s climate, including the intensity and duration of the glacial cycles.
However, during the mid-Pleistocene transition, which occurred between 1.25 million and 700,000 years ago, the rhythm of the glacial cycles changed drastically.
Those cycles became colder and more extensive, extending from 41,000 years to 100,000.
The mid-Pleistocene transition, which has no obvious orbital cause, is still unexplained and difficult to find, since there are few “paleo-records” available about it.
The author of the research, Adam Hasenfratz, and his colleagues presented a new record of the temperature and salinity of the Southern Ocean 1.5 million years ago.
The experts analyzed the changes in that ocean during the transition of the Pleistocene by studying the oxygen isotopes enclosed in the microscopic shells of foraminifera, unicellular plactonic animals.
After confirming a reduction of the supply of deep water and a renewal of the existing one in the surface, the investigation suggests the appearance of a cycle of 100,000 years that coincided with a growing stratification of the ocean and a reduced ventilation of its bottom, where the water loaded with carbon dioxide it is transported to the surface and emitted into the atmosphere.
Consequently, the atmospheric carbon dioxide was reduced allowing the glacial periods to persist, despite the orbital rhythm drivers. (EFEUSA)