The slow rotation of the Earth and Mars’ orbits occurs every 2.4 million years. (representative)
Our existence is governed by natural cycles, from daily rhythms of sleeping and eating, to more long-term patterns, such as the passing of the seasons and the four-year cycle. leap year.
After studying seafloor sediments dating back 65 million years, we have discovered a previously undiscovered cycle to add to this list: the ebb and flow of deep ocean currents, linked to 2.4 million years of global warming and cooling is related to the expansion, while global warming and cooling are caused by the gravitational tug-of-war between Earth and Mars.Our research is Published in Nature Communications.
Milankovitch cycles and ice ages
Most of the natural cycles we know of are determined in some way by the movement of the Earth around the Sun.
as the german astronomer Johannes Kepler It was first recognized four centuries ago that the orbits of Earth and the other planets are not exactly circular, but rather slightly squashed ovals. Over time, the gravitational collisions of planets change the shape of these orbits in predictable patterns.
These changes affect our long-term climate, influencing the onset and end of ice ages. 1941, Serbian astrophysicist Milutin Milankovic Recognize that changes in the shape of the Earth’s orbit, the tilt of its axis, and the wobble of the poles all affect the amount of sunlight we receive.
as. . And be known”Milankovitch cycle” These patterns occur with periods of 405,000, 100,000, 41,000, and 23,000 years. Geologists have found traces of them in Earth’s distant past, even in 2.5 billion year old rocks.
Earth and Mars
There are also slower rhythms, called astronomical “macrocycles,” that cause fluctuations over millions of years. Such a cycle, related to the slow rotation of the orbits of Earth and Mars, occurs every 2.4 million years.
The cycle forecast is astronomical modelbut rarely found in the geological record. The easiest way to find it is in sediment samples that have been continuously covered for millions of years, but this is rare.
Like the shorter Milankovitch cycle, this large cycle affects the amount of sunlight the Earth receives and has an impact on the climate.
gaps in records
When we look for signs of these multimillion-year climate cycles in the rock record, we use a “big data” approach. Scientific ocean drilling Data collected since the 1960s have produced a treasure trove of information on deep-sea sediments from all periods in the world’s oceans.
Our research was published in nature communicationswe used sedimentary sequences from more than 200 drilling sites to discover previously unknown connections between Earth and Mars orbital changes, past global warming cycles, and acceleration of deep ocean currents.
Most studies focus on complete high-resolution records to detect climate cycles. Instead, we focus on missing parts of the sedimentary record—disruptions in deposition known as hiatus.
Deep-sea discontinuities indicate violent seafloor currents eroding seafloor sediments. Instead, continued sediment accumulation suggests calmer conditions.
By analyzing the timing of global ocean hiatus, we identified hiatus cycles over the past 65 million years. The results show that the intensity of deep ocean currents changes with the shape of the Earth’s orbit on a 2.4 million-year cycle.
Astronomical models show that the interaction between Earth and Mars drives a 2.4 million-year cycle in which more sunlight and a warmer climate alternate with less sunlight and a cooler climate. Warmer periods are associated with more deep-ocean discontinuities and are associated with stronger deep-ocean currents.
Warming and deep ocean currents
Our results are consistent with recent satellite data and ocean model Map short-term changes in ocean circulation. Some show that ocean mixing has become more intense during global warming over the past few decades.
deep sea vortex It is expected that in a warmer, more dynamic climate system, especially high latitudes, as major storms become more frequent. This makes deep-sea mixing more intense.
Deep-sea eddies are like giant wind-driven whirlpools that often reach the deep ocean floor.They cause seafloor erosion and the accumulation of massive sediments, called Contour driftsimilar to a snowdrift.
Could Mars keep oceans alive?
Our results extend these insights to longer time scales. Our deep-sea data spanning 65 million years show that warmer oceans have more active eddy-driven circulation.
This process may play an important role in future warming. In a warming world, the temperature difference between the equator and the poles shrinks.This resulted in weaken in the world Marine conveyor belt.
In this case, oxygen-rich surface water will no longer mix well with deeper waters, potentially causing stagnant ocean.Our results and Deep sea mixing analysis suggest that stronger deep-sea eddies may counteract this ocean stagnation.
How Earth-Mars astronomical influences interact with shorter Milankovitch cycles and current human-driven global warming will depend heavily on the future trajectory of our greenhouse gas emissions.
(author:Adriana DutkiewiczARC Future Fellows, University of Sydney; Dietmar Müllerprofessor of geophysics, University of Sydneyand Sla BlilaAssociate Lecturer, Sorbonne University)
(Disclosure statement:Adriana Dutkiewicz receives funding from the Australian Research Council. Dietmar Muller and Slah Boulila do not work for, consult, own shares in, or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant relationships beyond their academic appointments)
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