Ancient Clays of Mississippi reveal the dramatic saga of Antarctic ice on prehistoric Earth

New research shows that mud cores excavated in Mississippi hold long-hidden clues about the origins of Antarctica’s giant ice sheets some 34 million years ago in Earth’s history.

Earth was in the middle of a Great transmission At that time, passing is enjoyable Eocene era to the coldest from the Oligocene. Universe There was no ice It was permanent during the Eocene, but by the beginning of the Oligocene it already had ice sheets 25% bigger than those we know today.

As these ice sheets grew during the Eocene-Oligocene transition, sea levels also dropped by about 40 meters (131 ft), exposing previously submerged areas of land in the wake of coastal retreat.

This dramatic drop in sea level has resulted in large amounts of carbon being removed from the atmosphere coastal sediments in the atmosphere, according to the research team’s analysis of ancient clays from the same period collected near Jackson, Mississippi.

“We’ve unearthed information from Mississippi mud to answer a key question about how the Antarctic ice expanded so dramatically to the continental scale.” she says Senior author Tom Dunkley-Jones, microbiologist and paleontologist at the University of Birmingham, UK.

The study authors note that these Antarctic ice sheets originally formed due to the long-term burial of carbon in sediments, sequestering it away from the atmosphere, where it is known to have heat retention effect.

They add that this decrease in atmospheric carbon also allowed Earth’s transition on a larger scale to the coldest modern climate in the past 34 million years, creating cooler conditions that helped create massive ice sheets in Antarctica, which in turn led to a drop in global sea levels. .

This all happened too quickly for many species to adapt, resulting in a catastrophic event widespread mass extinction, as previous research has shown. that turbulent period It is also known by the French nickname Grande Coupure, which means “great cut”.

“The transition from the Eocene to the Oligocene was probably the largest climate cooling event on the planet and had a significant impact on Earth’s history.” she says Dunkley Jones.

However, amid this general cooling trend, lower sea levels caused by Antarctic glaciation also led to another opposite trend, Dunkley-Jones and colleagues report.

Ocean retreat has exposed large areas of coastal sediment, making them highly vulnerable to erosion. These soft, submerged sediments contain large amounts of plant material and other organic debris, which are no longer protected by sea water.

As these mangrove-like habitats dried up, their heritage of organic matter was exposed to oxygen and became a feast for microbes, which released trapped carbon into the atmosphere in the form of carbon dioxide.

This increase in carbon dioxide _{He was} enough to cause a “negative transient climate cooling reaction”, Type researchersbriefly undermining the planet’s climate transition”ice house“.

“As sea levels drop during this transition period, we could see a temporary restraint in atmospheric cooling with the release of large amounts of trapped carbon dioxide in coastal areas around the Mississippi River basin.” she says Dunkley Jones.

The team notes that the transfer of carbon from these coastal sediments may not have halted the planet’s progression to a cooler Oligocene climate, but it does reveal important details about how this complex system works.

“Our research gives us valuable new evidence about how Earth’s climate can undergo dramatic changes and how this is often strongly linked to the biosphere and the carbon cycle.” she says Kirsty Edgar is a microbiologist and paleoanthropologist at the University of Birmingham.

The study examined marine mud from a depth of about 137 metres, and compared the data it received with evidence about the transition from the Eocene to the Oligocene from elsewhere, particularly the Pacific Ocean.

This revealed long-term changes in sediment accumulation, the researchers explained, highlighting the timing of the sea-level drop that coincided with the formation of the ice sheets.

“Understanding these past events gives us a clearer picture of the beauty and complexity of Earth’s climate and environment.” she says e d g a y

The study was published in Nature Communications.

By Russell McClendon
Posted in Science alert