Why did the ice cycle intensify a million years ago?
About a million years ago, a great event happened on the earth. The Earth’s climate system has undergone a major shift in response to changes in our orbit around the sun.This transformation is called Mid-Pleistocene transitionBefore MPT, the cycle between glacial (cold) and interglacial (warmer) periods occurred every 41,000 years. After the MPT, the ice age became more intense—strong enough to form an ice sheet that lasted 100,000 years in the northern hemisphere. This provides the earth with a regular ice age cycle that continues into the human age.
For a long time, scientists have been confused about the causes of this situation.One possible reason is a kind of Milankovic cycle-Periodic changes in the earth’s orbit and the direction towards the sun will affect the energy absorbed by the earth. Scientists agree that this has been the main natural driving factor for the alternation of cold and warm for millions of years. However, research shows that the Milankovitch cycle did not change much a million years ago, so there may be other factors at play.
In line with MPT, a large ocean current system that helps transfer heat globally has experienced a severe weakening.The system that sends heat north through the Atlantic Ocean is Atlantic meridional overturning circulation (AMOC). Is this slowdown related to the transition of the ice age? If so, how and why? These are open questions.A new paper published in the journal today Proceedings of the National Academy of Sciences An answer was proposed.
A new study shows that one million years ago, glaciers began to stick to their beds more persistently, triggering a longer ice age cycle. Here, ice flows from the Breiðamerkurjökull glacier in Iceland to the Atlantic Ocean. (Kevin Krajic/Earth Institute)
Researchers analyzed deep-sea sediment cores collected in the South Atlantic and North Atlantic, where ancient deep waters flowed through and left chemical clues. “We found that just before this crash, the behavior of the North Atlantic was very different from the rest of the basin,” said the lead author and Maayan Yehudai, who worked on this work during his PhD. A student at Columbia University’s Lamont-Dougherty Earth Observatory.
Before the ocean circulation collapsed, ice sheets in the northern hemisphere began to stick to the bedrock more effectively. This causes the glacier to become thicker than before. This, in turn, led to greater global cooling than before, and disrupted the Atlantic Thermal Energy Belt. Yehudai said that this led to a more intense ice age and a shift in the ice age cycle.
The study supports a long-argued hypothesis that the accumulated slippery continental soil was gradually removed during the previous ice age, allowing the ice sheet to adhere more closely to the older and harder crystalline bedrock below and become thicker and thicker. more stable. The survey results show that just before the weakening of AMOC, this growth and stability affected the global climate.
“Our research solves one of the biggest problems of climate change since the beginning of the ice age,” Yehuday said. “This is one of the most significant climate shifts, and we don’t fully understand it. Our discovery fixed the origin of this change in the northern hemisphere and the ice sheet that evolved there, because it pushed this to the climate we observe today. The transformation of the model. This is a very important step in understanding its causes and sources. It highlights the importance of the North Atlantic region and ocean circulation to current and future climate change.”
The research was also led by Yehudai’s consultant, Lamont geochemist Steven Goldstein (Steven Goldstein) and Lamont graduate student Joohee Kim. Other collaborators include Karla Knudson, Louise Bolge and Alberto Malinverno of Lamont-Doherty; Leo Pena and Maria Jaume-Segui of the University of Barcelona; and Torsten Bickert of the University of Bremen. Yehudai is now at the Max Planck Institute of Chemistry.
