Mars gravity drives ocean currents on Earth

Geological records of deep-sea currents have revealed a connection between the orbits of Earth and Mars, which has apparently impacted on past global warming events and even ocean circulation.

An analysis published in Nature Communications shows a 2.4-million-year cycle of waxing and waning deep currents. This ebb and flow is linked to periods of increased energy from the Sun and warmer global climates (completely unrelated to other triggers of climate change such as human emission of greenhouse gases).

Data from hundreds of drilling sites around the world collected over more than 50 years revealed  the speed of deep-sea currents shifts every couple of million years.

“We were surprised to find these 2.4-million-year cycles in our deep-sea sedimentary data,” says lead author, the University of Sydney’s Dr Adriana Dutkiewicz. “There is only one way to explain them: they are linked to cycles in the interactions of Mars and Earth orbiting the Sun.”

So, Earth’s attraction to Mars causes deep rumblings in our planet’s deep-sea currents. It’s almost romantic.

“The gravity fields of the planets in the solar system interfere with each other and this interaction, called a resonance, changes planetary eccentricity, a measure of how close to circular their orbits are,” says co-author Dietmar Müller, a professor also from the University of Sydney.

This gravitational interplay has meant that Earth has a higher level of solar radiation and warmer climate every 2.4 million years. Warmer cycles correlate to breaks in the deep-sea record due to more vigorous deep ocean circulation.

Ocean currents play a major role in the climate in different parts of the world.

For example, the Atlantic Meridional Overturning Circulation (AMOC) is part of the global ocean “conveyor belt” which carries water from north to south and back. It takes warmer water into cooler latitudes, keeping Europe temperate, and transports vital nutrients to sustain marine life.

Recent research suggests that AMOC has weakened by about 15% since 1950 and is at its weakest in more than a thousand years. This is attributed to cold freshwater entering the Atlantic Ocean in large volumes, including from the melting Greenland Ice Sheet.

It is possible the 2.4-million-year cycle of the deep-sea currents could act as a counterweight to the AMOC’s faltering. “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,” says Müller.

“Our deep-sea data spanning 65 million years suggest that warmer oceans have more vigorous deep circulation,” adds Dutkiewicz. “This will potentially keep the ocean from becoming stagnant even if Atlantic Meridional Overturning Circulation slows or stops altogether.”

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