The influence of orbital parameters on Earth’s climate is well established. These are the famous Milankovitch cycles. However, other larger-scale astronomical interactions could also govern the establishment of warm periods. This is notably the case of the orbital resonance between Earth and Mars. A new study shows that this forcing, which occurs every 2.4 million years, could even influence deep ocean circulation.
Throughout its history, Earth has experienced numerous climate variations. Most of them show a cyclicality of about 10,000 to 100,000 years, which is linked to the evolution of certain orbital parameters, such as eccentricity (variation in the shape of Earth’s orbit), obliquity (variation in the tilt of the rotation axis), and precession of the equinoxes (variation in the orientation of the rotation axis). This astronomical forcing induces cyclical variations in insolation, which govern Earth’s climate. These are known as the Milankovitch cycles.
Earth’s climate influenced by Mars every 2.4 million years
However, sedimentary records indicate the existence of larger-scale paleoclimatic cycles. These would be linked not to variations in the astronomical parameters of the Earth-Moon system, but to large cycles involving other planets of the Solar System. Evidence of these cycles, spanning millions of years, is much rarer, and this forcing phenomenon is much less constrained than the Milankovitch cycles.
Several studies have already noted the existence of a 2.4-million-year cycle, which would be related to an interaction between the orbits of Earth and Mars. It appears that the orbits of the two planets regularly enter into resonance, affecting their eccentricity. Every 2.4 million years, Earth would thus find itself closer to the Sun, a situation that leads to a period of climate warming.
A new study by researchers from the University of Sydney and Sorbonne University reveals that this astronomical interaction between Mars and Earth could even have affected the deep ocean currents of our planet.
Mars regularly disrupts deep ocean currents through climate warming
Scientists analyzed the organization of sedimentary layers deposited in deep-sea environments over the last 70 million years. They identified 387 interruptions in sedimentation, indicating episodes of seafloor erosion and reorganization of deep-sea currents. These events occurred cyclically… approximately every 2.4 million years! Comparison with astronomical models reveals that this cyclicity is indeed associated with the orbital interactions between Mars and Earth.
These results, published in the journal Nature Communications, suggest that global warming induces an intensification of deep ocean circulation. If in the past these warm periods have been governed by Earth’s orbital parameters or interactions with other celestial bodies like Mars, the same link between climate and deep ocean currents can be assumed for the present and future, even if the causes of warming are different. These findings could help better understand how the ocean will respond to current climate warming.
Previously, models suggested that in the face of climate warming, the Atlantic current system (Amoc), which is responsible for the famous Gulf Stream, could weaken or even disappear. This new study proposes that this phenomenon could be counteracted by the development of new and powerful deep currents.