© AFP 2018 / Eitan AbramovichТюлень on the ice in Antarctica© AFP 2018 / Eitan AbramovichПодпишись to daily updates RIA Science
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. The earth came forth from the endless cycle of glaciations and warming, and mankind has the ability to create a civilization because of increasing currents and «escape» the great mass of the CO2 from the waters of the southern oceans of the Earth. Write about paleoclimatology in the journal Nature Geoscience.
«I think we found the answer to this interesting historical mystery. Strengthening of the currents in the southern oceans of the Earth have allowed the carbon dioxide gas contained in their waters to escape into the atmosphere and heat the planet. Got there a very small amount of CO2, but it was enough to stop cooling and the dawn of civilization,» said Daniel Sigman (Sigman Daniel) from Princeton University (USA).
The last glacial period in Earth’s history, how geologists now believe, began about 2.6 million years ago. Its main feature is that the area of glaciation and surface temperature of the Earth during its period were not constant.
Glaciers advancing and retreating every 40 and 100 thousand years, and these episodes were accompanied by a sharp cooling and warming. The last warming period began about 13 thousand years ago and is still ongoing.
These cycles of glaciations and «thaws,» as many scientists now believe, primarily associated with the so-called Milankovitch cycles – «wobble» of the Earth’s orbit that change how much heat is getting poles and temperate latitudes. Other geologists and climatologists believe that in fact these abrupt climate changes are not associated with «space», but it is earthly factors such as the restructuring of the «conveyor belt» of currents in the oceans or the increase or decrease of the share of CO2 in the atmosphere.
Scientists for quite a long time arguing about whether the left the Earth from this cycle of glaciations and warming, or the current «thaw» is part of these long-term fluctuations. For example, proponents of the first group of theories suggest that the climate of the planet irreversibly changed 20-15 thousand years ago, volcanic eruptions or other catastrophic events, the release of large quantities of CO2 into the atmosphere.
Sigman and his colleagues have uncovered the reason for these changes by studying the rock samples extracted from the bottom of the southern parts of the Indian, Pacific and Atlantic oceans. Beyond the rocks, climatologists have analyzed changes in the rate of growth of coral reefs existing in their territory for thousands of years.
Analyzing the proportion of nitrogen isotopes in these sediments, the researchers tried to assess how much organic matter and carbon dioxide were at the bottom and in deep ocean waters, and how many of them returned to the surface. As a rule, the smaller the proportion of «heavy» nitrogen-15, the more organic matter and CO2 had to escape from the depths of the ocean and into the Earth’s atmosphere one way or the other.
It turned out that the proportion of nitrogen-15 decreased gradually throughout the Holocene, the last geological era that started about 13-14 thousand years ago. During this time, the concentration of heavy nitrogen fell 0.2%, which is equivalent to increasing the proportion of CO2 in the atmosphere of 20 parts per million, or about 7% of its concentration in dobromyslova era.
That could speed up the «escape» of organic matter and CO2 from the deep ocean floor? Scientists assume that this phenomenon was associated with the strengthening of westerlies and accelerating the movement of currents in temperate and Subpolar waters of the Indian, Pacific and Atlantic oceans.
Due to this the temperature of the Earth has remained consistently high over the last 13 thousand years and not gradually falling, as occurred in previous interglacial periods. It allowed humanity to move to a settled way of life and create a civilization, the authors conclude the article.