Scientists have long since discovered that during the ice ages on Earth the carbon dioxide contained in the atmosphere was regularly lower, by about a third, compared to the warmer phases. There is no complete explanation about this effect and various theories have been created over time to explain their causes.
One of the most popular theories goes back to the oceans: during the cold ages and the ice ages, the seas cooled, more or less at the same rate (their temperature decreased by approximately 2.5 °C) and this caused a greater release of carbon dioxide in the air since the water, when it is colder, shows a greater degree of solubility of the CO2.
However, the models that refer to this theory show that the cooling of the seas was responsible for only a few percentage points with respect to the reduction of carbon dioxide in the atmosphere.
The mystery seems to have been solved by a new study published in Science Advances.
According to Andreas Schmittner, climatologist of the State University of Oregon, in reality the oceans, during the ice ages, would have cooled to a level much higher than previously theorized. The cooling of the water was such that it represented at least 50% of the causes that led to the decrease of CO 2 in the air.
Another third is represented by the increase in iron-laden dust in the seas, which led to an increase in the presence of phytoplankton which absorbed more carbon making it deposit on the seabed.
The seas increased the presence of iron as this, in the form of very fine dust, came from the continents and from the increase in ice in various regions of the world which in turn caused the release of iron from rocks and soil.
Adding together the two factors relating to the seas (cooling and increase in iron dust), we therefore explained, according to this study, at least three-quarters of the causes that led to the increase of CO2 in the atmosphere.