Millions of years ago, after the extinction of the dinosaurs flightless, The amount of atmospheric carbon dioxide (CO₂) was drastically reduced, so our climate planet It became colder.
Most studies in this regard indicate that it was due to a series of phenomena, among which the weathering (the process by which rocks weather and decompose).
However, a new scientific article revealed that Another element, present in maritime water, would also have been key to the reduction of CO₂ and, consequently, to the cooling of the Tierra.
Rock erosion and slow ocean floor expansion: classic explanations for temperature reduction
Recently, the results from an investigation carried out by a team of 14 scientists led by David Evans, from the School of Ocean and Earth Sciences, Southampton, UK.
These, which were published in the American magazine Proceedings of the National Academy of Sciences, They could change the interpretation about why, millions of years ago, the temperature of our planet decreased.
66 million years ago, when the dinosaurs They inhabited these lands, the weather was 5 to 10 degrees warmer than the current one, according to estimates.
However, in the first stage of the Cenozoic era, When these gigantic animals had disappeared, the atmospheric concentration of CO₂ was drastically reduced, which caused the Earth to gradually cool.
Since CO₂ retains heat, its decrease caused the appearance of permanent ice and the relatively stable climate in which humanity evolved.
Traditionally, Most scientists explained this drop in CO₂ by arguing that it was mainly due to changes in weathering. of silicates (the chemical erosion of continental rocks).
Silicate weathering consumes CO₂ from the atmosphere and locks it into rocks over the long term, meaning there is less of this chemical on the Earth’s surface.
Other researchers propose a different explanation (or complementary), related to the fact that, at said stage, The ocean floor expanded more slowly than usual.
This phenomenon is known as «underwater volcanic activity,» and when it occurs it releases carbon dioxide to the surface.
Therefore, if there is less underwater volcanic activity, less CO₂ is released from the Earth’s interior and, therefore, atmospheric carbon dioxide decreases.
«An approximately 5-fold decrease in atmospheric CO₂ concentration took place during the Cenozoic. This has often been seen in the context of silicate weathering changes […] It has alternatively been argued that changes in the rate of seafloor spreading contributed to the decline of p CO₂ in the Cenozoic,» the article explains.
However, those who prepared the document believe that «[…] The magnitude of the decrease means that ‘it is unlikely’ that this (the mentioned phenomena) explains the entire change of p CO 2 (partial pressure of carbon dioxide)».
Therefore, these scientists set out to study the chemical elements of sea waterwith the intuition that they may also have contributed to the decrease in atmospheric carbon dioxide and, therefore, to the decrease in the temperature of our planet.
Calcium, an unexpected cause
The authors of the article maintain that the change in the composition of the main chemical elements of seawater, especially calcium concentrationwas always overlooked in this type of studies, since it was believed that it simply reacted to weathering processes, and not that It could be an element causing the decrease in carbon dioxide on Earth.
Consequently, they carried out an in-depth investigation by which they verified that lat calcium concentration [Ca 2+ sw] has the potential to control key processes that impact the carbon cycle.
Until now, it was believed that the concentration of maritime calcium occurs through processes such as weathering, which releases calcium that can reach the sea.
The logic was that a terrestrial event changed the amount of calcium in the oceans, and not that an oceanic event could modify the reality of the Earth.
On the contrary, the recent study revealed that Calcium may play an active role in an Earth process, specifically atmospheric CO₂ levels.
The explanation for this is that, when it enters the ocean, carbon dioxide is transformed into carbonate.
Then, if the water source has a lot of calcium, a combination occurs that shapes the calcium carbonate (CaCO₃).
This chemical accumulates in marine sediments and, therefore, The carbon dioxide that makes it up stays there for a long time, relegating its function as a heat receptor on the Earth’s surface.
Therefore, the authors say, This process may have contributed to the drop in Earth’s temperature, which happened in the era immediately after the dinosaurs.
However, they clarify, its level of influence is difficult to determine, since it would be necessary to know exactly that of the other phenomena that also removed atmospheric CO₂, mainly weathering.
