Sciences. Tectonic shift in the Southern Ocean caused Antarctica to freeze

Madrid, 24 (European Press)

The sudden cooling that occurred 34 million years ago that contributed to the formation of the Antarctic ice sheets had a tectonic origin.

High-resolution simulations of ocean cycles show that the tectonic opening of the Southern Ocean sea lanes caused a fundamental reorganization of ocean currents, heat transfer, and resulted in a strong cooling of Antarctic surface waters by up to 5 °C.

The study, by an international team of researchers from the University of Leicester, the Netherlands, Australia, Germany and Norway, is published in the journal Nature Communications. The findings shed new light on a 50-year-old question about how and why the Antarctic ice sheets formed.

Dr Katharina Hochmuth, Research Associate at the International Ocean Discovery Program (IODP) at the University of Leicester and co-author of the study, said in a statement: “In the past week and in the run-up to COP26, we heard a lot about modeling projections about the future of our planet. It is necessary to include atmospheric carbon dioxide conditions, as well as appropriate geographic regions from the past, to successfully model climate change.

“A change of 600 meters in ocean gate depth could cause a sharp drop in coastal temperatures and thus the fate of the Antarctic ice sheet.”

The last terrestrial bridges connecting Antarctica to the surrounding continents, Australia and South America, were broken about 34 million years ago. Not only did this tectonic event leave Antarctica isolated from other land masses; It also led to a major reorganization of ocean currents in the Southern Ocean.

A polar ocean current began to flow, preventing sub-polar eddies from transporting warm surface waters to the Antarctic coast. At the same time, ice sheets began accumulating in Antarctica and Earth experienced one of the most fundamental climate change events, transitioning from warming to ice-cold conditions.

The authors’ high-resolution ocean simulations show that just a small deepening of the Southern Ocean’s sea lanes by a few hundred meters resulted in a significant cooling of Antarctica’s surface waters. Besides declining atmospheric carbon dioxide concentrations, this tectonic event played an important role in the first Antarctic Ice Age and in the Earth’s transition to the ice world.

The results presented in this study demonstrate the importance of tectonic-driven processes in the changing oceanographic and climatic conditions of the Southern Ocean.

Understanding these ancient climate stages is critical to validating climate models that predict future climate conditions and understanding how the climate might behave at high concentrations of atmospheric carbon dioxide (CO2).