Accompanying the MPT, a large system of ocean currents that helps move heat around the globe experienced an extreme weakening. That system, which sends heat north through the Atlantic Ocean, is the Atlantic Meridional Overturning Circulation (AMOC). Was this downturn associated to the shift in glacial durations? If so, how and why? These have been open questions. A new paper published on November 8, 2021, in the journal Proceedings of the National Academy of Sciences proposes an answer.
The researchers evaluated cores of deep-sea sediments taken in the north and south Atlantic, where ancient deep waters gone by and left chemical ideas. “What we discovered is the North Atlantic, right prior to this crash, was acting really in a different way than the remainder of the basin,” said lead author Maayan Yehudai, who did the work as a PhD. trainee at Columbia Universitys Lamont-Doherty Earth Observatory.
Prior to that oceanic circulation crash, ice sheets in the Northern Hemisphere began to stick to their bedrock more effectively. This led to both stronger ice ages and the ice-age cycle shift, states Yehudai.
The research supports a long-debated hypothesis that the gradual removal of accumulated slippery continental soils during previous ice ages enabled ice sheets to cling more securely to the older, harder crystalline bedrock underneath, and grew thicker and more steady. The findings indicate that this growth and stabilization prior to the weakening of the AMOC formed the global environment.
” Our research addresses one of the biggest questions about the largest environment change we had given that the onset of the ice ages,” said Yehudai. Our discovery pins the origin of this modification to the Northern Hemisphere and the ice sheets that progressed there as driving this shift towards the climate patterns we observe today.
Reference: “Evidence for a Northern Hemispheric trigger of the 100,000-y glacial cyclicity” by Maayan Yehudai, Joohee Kim, Leopoldo D. Pena, Maria Jaume-Seguí, Karla P. Knudson, Louise Bolge, Alberto Malinverno, Torsten Bickert and Steven L. Goldstein, 8 November 2021, Proceedings of the National Academy of Sciences.DOI: 10.1073/ pnas.2020260118.
The research was led also by Yehudais consultant, Lamont geochemist Steven Goldstein, in addition to Lamont graduate trainee Joohee Kim. Other collaborators consisted of 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 for Chemistry.
A new study recommends that a million years earlier, glaciers began sticking more constantly to their beds, activating cycles of longer ice ages. Here, ice released from Icelands Breiðamerkurjökull glacier on its method to the Atlantic ocean. After the MPT, glacial durations became more intense– extreme adequate to form ice sheets in the Northern Hemisphere that lasted 100,000 years.” Our research study addresses one of the biggest concerns about the largest environment change we had given that the start of the ice ages,” stated Yehudai. Our discovery pins the origin of this change to the Northern Hemisphere and the ice sheets that progressed there as driving this shift towards the climate patterns we observe today.
A brand-new study recommends that a million years ago, glaciers started sticking more constantly to their beds, triggering cycles of longer glacial epoch. Here, ice discharged from Icelands Breiðamerkurjökull glacier on its method to the Atlantic ocean. Credit: Kevin Krajick/Earth Institute
Why did glacial cycles magnify a million years back? Researchers find ideas on the bed of the Atlantic Ocean.
Something huge happened to the world about a million years earlier. There was a significant shift in the action of Earths climate system to variations in our orbit around the Sun. The shift is called the Mid-Pleistocene Transition. Prior to the MPT, cycles between glacial (chillier) and interglacial (warmer) periods happened every 41,000 years. After the MPT, glacial periods became more intense– extreme enough to form ice sheets in the Northern Hemisphere that lasted 100,000 years. This offered Earth the regular ice-age cycles that have persisted into human time.
Scientists have actually long puzzled over what activated this. A likely reason would be a phenomenon called Milankovitch cycles– cyclic modifications in Earths orbit and orientation towards the Sun that impact the amount of energy that Earth absorbs. This, scientists agree, has actually been the primary natural driver of alternating cold and warm periods for millions of years. Research has shown that the Milankovitch cycles did not undergo any kind of huge modification a million years earlier, so something else likely was at work.
