Mars’ gravity may be strong enough to influence Earth’s deep-ocean currents

Signs that Mars’ gravity is affecting Earth’s climate have been found in sediments on the deep ocean floor. Long climate cycles caused by resonance between the two planets’ orbits have been predicted by models, but geological evidence is scarce. The scientists who have noticed this pattern are wary of jumping to conclusions, but say it could mean there is less danger to the deep oceans from humanity’s climate vandalism than feared.

Mars is a small planet, and although it is relatively close, its gravitational effects on Earth are small. However, in the long run, little things can become important. “The gravitational fields of the planets in the solar system interfere with each other and this interaction, called resonance, changes the planets’ eccentricity, a measure of how close their orbits are to a circle,” says Professor Dietmar Müller of the University of Sydney. rack.

These changes mean that Earth experiences periods of more and less sunlight over a 2.4 million year cycle, similar to those produced by the much shorter Milankovich cycles. Although the changes in the sunlight Earth received during these cycles are subtle, Müller told IFLScience that amplifying factors are expected to cause the planet to warm and cool significantly on this time scale.

Detecting such cycles is difficult when there are so many other factors determining global and local climate, and few examples have been found in the geological record. However, Müller and colleagues have found a cycle in the deep oceans that fits well with the predicted time scale. On the ocean floor, they found gaps, known as gaps, when sediment stopped accumulating, and these occur over a period of 2.4 million years.

Müller and colleagues say the gaps are the result of the strengthening of eddies in the deep ocean, which scour the seafloor so sediments can’t build up. The eddies are driven by the wind. Warmer periods release more energy into the atmosphere, which strengthens the wind and gives the vortices enough force to scour the ocean floor, the team suspects, all because of small forces from Mars.

If the authors are right, this could be rare good news for the future of the planet. If warmer conditions create more powerful vortices, the extra heat trapped by humanity’s gases could cause a similar improvement. “There are signs that this is already happening,” Müller told IFLScience, with wind-driven currents apparently strengthening, particularly the Antarctic Circumpolar Current.

That would be welcome, because a feared consequence of higher temperatures is a stagnant deep ocean. Without any force to move it, the oceans would tend to stratify, with oxygen-rich water at the top and colder water confined to the depths. The eddies that Müller and colleagues investigate are one of the two main forces preventing this. The other, known as the global thermohaline system or the Atlantic Meridional Overturning Circulation (AMOC), works in very different ways and is suspected of weakening due to reduced Arctic sea ice formation.

The AMOC is sometimes described as the turnoff of the Gulf Stream.

If AMOC were to weaken, let alone collapse as feared, the increased stratification could have several disastrous consequences. First, it would hinder the oceans’ ability to suck carbon dioxide to the depths, where it does little damage. The loss of deep-water oxygen could also extend the global extinction event to the only region we can expect to be safe. Rising cold waters are bringing nutrients, creating the most fertile fishing grounds on Earth, and this could stop too. Finally, the global thermohaline system redistributes heat across the planet, and without it some areas would warm even faster.

Müller’s vortices could counteract at least the first three of these, although Müller admitted to IFLScience that how quickly and to what extent questions are beyond the scope of this study. “Of course, this would not have the same effect as AMOC in terms of transporting water masses from low to high latitudes and vice versa,” he acknowledged in the statement.

Because Earth is more massive than Mars, our planet’s gravity should have an even greater effect on the Red Planet’s orbit. Müller told IFLScience that he doesn’t know what climatic effects this might have caused there, or whether we could find any evidence of that.

The research is open access in Nature Communications.

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