Scientists from Australia and France claim to have discovered an incredible connection: Mars sets the pace for climate fluctuations on Earth as well as the increase and decrease of huge deep-sea currents in a cycle of 2.4 million years. They think they can read this from marine deposits. You now have your results in a specialist journal Nature Communications published.
Sedimentologist Adriana Dutkiewicz from the University of Sydney originally wanted to find out how the strength of deep-sea currents has evolved over time. To do this, she and Dietmar Müller from the University of Sydney and Slah Boulila from Sorbonne University analyzed sediment deposits from the deep sea that go back 65 million years. These had been collected since the 1960s and came from almost 300 boreholes from all of the world’s oceans.
Sometimes the Earth draws perfect circles around the sun, sometimes it follows an elliptical orbit
The spectral analysis revealed a remarkable pattern: at relatively regular intervals, they discovered geological layer gaps, so-called hiates. In other words, periods of time for which no corresponding sediment layers were found. The research team assumes that huge deep-sea eddies once eroded away the deposited layers. In a cycle of around 2.4 million years, the vortices first swelled and then subsided again.
This coincides surprisingly well with another cycle: the earth does not always revolve uniformly around the sun; sometimes it draws a perfect circle around the central celestial star, sometimes it follows an elliptical path. Then the eccentricity – the measure of the deviation from the circular shape – is particularly large. And this interplay occurs in cycles of different lengths – the longest and most dominant of which lasts 2.4 million years.
Geoscientists suspect the origin of this to be the tug of war between two planets: Mars and Earth. “The gravity fields of the planets in the solar system interfere with each other,” explains geophysicist Müller. “And this interaction, called resonance, changes the eccentricity of the planets.” And with it the climate on Earth: The more the Earth’s orbit around the sun deforms and becomes more oval, the more pronounced the seasons and the greater the solar radiation at certain times of the year. During a maximum eccentricity, the world is on average 1.75 degrees Celsius warmer than during a minimum eccentricity, according to the report Nature Communications Study.
Dutkiewicz’s team concludes from their observations that the huge whirlpools were always particularly active during warm climate conditions. This could have been of great importance for life in the deep sea in the past, as the deep sea eddies probably ensured that the world’s oceans were kept aerated – even when important current systems broke down in the warm climate; like the Atlantic Overturning Current, a gigantic water conveyor belt that supplies Europe with large amounts of warm water from the tropics. “The geology of the deep sea provides us with valuable insights into how the oceans function in a warmer world,” says Müller.
And that is of interest right now. Some climate researchers believe it is possible that the Atlantic overturning current could come to a standstill again this century or the next as a result of man-made climate change. In that case, one could follow the arguments of the authors Nature Communications Study – at least the deep sea eddies step in and save the oceans from stagnating and turning into dead zones. Actually, the next eccentricity maximum can only be expected in a million years. But because humans are warming the planet as if in fast motion, the deep sea eddies are also becoming active more quickly, argues Müller. Satellite observations have already shown that the oceans have been mixing more intensively for a few decades.