An international group of scientists from Tasmania, Great Britain, the Netherlands and Norway disclosed the reason for global cooling 34 million years ago, which led to the appearance of a thick glacial shield in Antarctica. According to the results of the study published in the journal Nature Communications, not only the reduction of carbon dioxide concentration in the Earth’s atmosphere, but also tectonic changes, which influenced the circulation of seawater in the southern ocean.
Traditionally it is believed that the change of hot greenhouse conditions on the cold climate in the early Cenozoic (from 52 to 34 million years ago) occurred due to a critical reduction in carbon dioxide in the atmosphere. These fundamental changes that determined the state of the modern climate of the Earth and known as the Eocene-oligocene transition (EOT) led to a decrease in the average surface temperature of the entire planet, expanding continental glaciers in Antarctica and the occurrence of an isolated ecosystem of Antarctic sea ice.
However, scientists will argue what role in EOT could play the lowering of the seabed, so that in the Southern Ocean, the Strait of Drakes, which is between Antarctica and South America, and the Tasmanian passage are marine waters between Australia and Antarctic. Because of this, the circumpolar antarctic course, enveling Antarctica and passing through all the meridians. This flow could act as a thermal insulator that prevents the heating of Antarctic. However, modern ocean models do not confirm that the transfer of heat to the shores of Antarctica did not occur at all; Consequently, the course did not seem to have to influence the cooling of the southern pole.
In the new work, researchers have developed an ocean model with a higher resolution than previous models that accurately reproduced the bottom relief in antiquity, and demonstrated that tectonics really played an important role in the reorganization of heat transfer in the Southern Ocean. If at least one sea pass (Tasmanian or Strait of Drake) had a depth of less than 300 meters, the marine cycle would transfer warm water to the banks of Antarctica. When the bottom dropped deeper than 300 meters deep, the cyphans were sharply weakened, which caused a cooling of surface waters by 2-5 degrees Celsius.
Scientists note that the fall in the level of carbon dioxide was likely to be a decisive factor in the growth of the Ice Cover of Antarctica. Nevertheless, tectonic processes also influenced the climate of the Southern Ocean and could set the CO2 concentration thresholds, below which the continent’s glaciation occurred. Thus, tectonics must be taken into account in future studies of climate sensitivity to greenhouse gases, the authors of the work are concluded.