Scientists of the Rice University in the United States revealed an unknown mechanism for reducing oxygen levels in the Earth’s atmosphere, which acted for 800 thousand years since late Pleistocene. This is reported in an article published in the journal Science Advances.
One of the main physicochemical processes consuming atmospheric oxygen is weathering sedimentary rocks. Another reason may be the oxidation of organic carbon contained under the glaciers for millions of years, but exposed when melting ice. The researchers analyzed ice cores, in which bubbles of ancient air were preserved, and showed that the oxygen content in the earth’s atmosphere fell by about 0.2 percent over the last 800 thousand years.
The oxygen level began to fall after the duration of glaciation on Earth doubled about a million years ago. These glaciations belong to the current glacial period, which began about 2.7 million years ago. During glacial eras, ice hats increased, covering to a third of the planet area, and then receded again to the poles. Since the duration of glacial cycles has increased more than doubled, the amount of sea level fluctuations increased.
Since as the glaciers are promoted, the level of the sea falls, the land area increases, which can be weathered. However, the contribution of this process, scientists estimated only in the fourth part of the observed drop in oxygen concentration. On the contrary, the consumption of oxygen caused by glacier erosion containing carbon rocks can explain the observed decline.