Research team: New findings on the formation of Antarctica

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The ice in West Antarctica appears to be reacting more strongly to global warming than the ice sheet in the east. An international research team led by the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI), attributes this to the origins of the ice: according to a new study, the Antarctic has frozen differently than previously assumed. According to the study, the ice sheet in the west is around seven million years younger than the eastern part.

Antarctica began to ice over around 34 million years ago as a result of climate change. At that time, the Earth changed from a greenhouse with only a few ice sheets to an "ice house with permanently glaciated areas", writes the team, which published its findings in the journal Science. How, when and from where the Antarctic ice sheet built up has not yet been precisely answered.

New deep-sea drill

The researchers analyzed a drill core that they had already taken in 2017 during the PS 104 expedition with the research icebreaker Polarstern off West Antarctica's Pine Island and Thwaites Glacier. They used a special drilling rig - the Marum-Mebo70 - to do this. The device, which was developed at the Center for Marine Environmental Sciences at the University of Bremen (Marum), is placed on the seabed from a ship and can drill around ten meters into the ground. Until now, the seabed at this point has been too compacted for conventional drilling methods.

During the first Antarctic glaciation around 34 million years ago, the region of the drill core apparently looked different. The researchers found no traces of ice. "This means that a large-scale, permanent first glaciation must have begun somewhere in East Antarctica," concludes Dr. Johann Klages, a geologist at the AWI who led the research team. Instead of glistening layers of ice, deciduous forests apparently covered West Antarctica. The cool, temperate climate prevented ice from forming there.

"This completely changes our knowledge"

Computer simulations and "complex modeling work" underpinned the researchers' thesis: they linked the new and already known data on air and water temperatures with the occurrence of ice. "This completely overturns our knowledge of the first Antarctic glaciation," says Gerrit Lohmann, paleoclimate modeler at the AWI.

Only in the coastal region of Northern Victoria Land in East Antarctica was the climate suitable for the formation of permanent ice. "Here, humid air masses encountered an intensively uplifting Transantarctic mountain range - ideal conditions for permanent snow and, as a result, for the formation of ice caps," the scientists write. From there, the ice sheet developed further into the East Antarctic hinterland. West Antarctica, on the other hand, remained ice-free for another seven million years until the climate here also allowed the area to freeze over.

Findings help to assess fundamental climate changes

Hanna Knahl, a paleoclimate modeler at the AWI, explains: "Our results make it clear how cold it had to get before the ice advance reached West Antarctica, many parts of which were already below sea level." The results also made it clear that the eastern and western parts of the Antarctic Shield reacted differently to external influences and climatic changes at the time of their formation: even a slight warming caused the western ice to melt - a phenomenon that scientists have already observed in recent years.

The team's findings have enabled a better understanding of the climate transition 34 million years ago. "Climate models can now grasp much more precisely what effects permanently glaciated areas have on global climate dynamics, i.e. the interactions between ice, ocean and atmosphere," explain the AWI team. Johann Klages sees enormous significance in the findings. "Especially in light of the fact that we could be facing such fundamental climate change again in the near future."

The research team consisted of scientists from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI), the British Antarctic Survey, Heidelberg University, Northumbria University in the UK and MARUM - Center for Marine Environmental Research, MARUM - Center for Marine Environmental Sciences at the University of Bremen and other partners from the Universities of Aachen, Leipzig, Hamburg, Bremen and Kiel, the University of Tasmania (Australia), Imperial College London (UK), the University of Leicester (UK), the Université de Fribourg (Switzerland), the Universidad de Granada (Spain), Texas A&M University (USA), Senckenberg am Meer and the Federal Institute for Geosciences and Natural Resources in Hanover.

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