2023-09-04 05:08:21
Mud cores from the Mississippi have revealed clues to the formation of Antarctica’s major ice sheets and a major climate cooling event, the Great Shutoff. The research suggests that falling sea levels exposed organic carbon in coastal sediments, leading to a 300,000-year delay in global cooling, as this carbon was released as carbon dioxide into the atmosphere.
Clues to the development of huge sheets of ice in Antarctica have been found in mud samples taken from Mississippi, shedding light on a major climate cooling event often called the Big Break or “great cut”.
A recent study in Natural Communicationsled by researchers from the University of Birmingham, examined material from core drilled near Jackson, Mississippi, USA.
Materials found in the core layers suggest that there was a major transfer of carbon from plant remains in coastal environments to the atmosphere, caused by a drop in sea level of about 40 meters during the formation of the Antarctic ice caps.
While the initial formation of these ice sheets and the onset of the colder modern climate of the past 34 million years was due to long-term burial or sequestration of carbon in sediments; the team found that falling sea levels caused a 300,000-year hiatus in global cooling.
The falling seas have exposed the coastal regions and their soft sediments to intense erosion due to rains and rivers. Organic carbon, like plant matter, that was once bound to these sediments and environments (think tropical mangroves today) was then exposed to oxygen in the air and was available for bacteria to eat. and convert it back to carbon dioxide which can be released into the atmosphere.
Dr Tom Dunkley Jones from the University of Birmingham is the lead author of the paper and said:
“We uncovered information about the Mississippi mud to answer a key question about how Antarctic ice massively expanded on a continental scale.
“The Eocene-Oligocene transition is probably the greatest climatic cooling event on the planet and has had a major impact on Earth’s history. As sea levels fell during this transition, we can observe how a temporary brake on atmospheric cooling occurred with the release of large amounts of carbon dioxide sequestered in coastal regions around the Mississippi River Basin. .
“This solves a puzzle about the timing of the transition and suggests that the beginnings of this event and the formation of the Antarctic ice sheets began some 300,000 years earlier. Once the organic carbon brake was exhausted, the transition was released to continue its evolution to the colder state of the last 34 million years.
The research team studied samples of marine clay covering a depth of around 137m – and compared them to other key records from this event, including those from the middle of the Pacific Ocean. The team was able to use data from the new samples to fill in gaps in the geological record, showing how sediments deposited in the area have changed over time and providing more accurate timings for the sea level drop that signaled the formation of ice caps. .
Dr Kirsty Edgar, University of Birmingham said:
“Our paper gives us a valuable new clue to how the Earth’s climate can undergo dramatic changes and how this is often strongly linked to the biosphere and the carbon cycle.
“Understanding these past events gives us a clearer picture of the beauty and complexity of Earth’s climate and ecology. »
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