The new findings show that glaciation in East Antarctica began 34 million years ago, in contrast to West Antarctica, which remained ice-free for much longer. The study highlights regional differences in the response of Antarctic ice to climate change.

Global warming has left its mark on the Antarctic ice sheets in recent years. Antarctica’s “eternal” ice is melting faster than previously thought, especially in West Antarctica. According to the findings of an international research team led by the Alfred Wegener Institute, the root of this may lie in its formation: Sediment samples from drilling cores, combined with advanced climate and ice sheet modeling, indicate that permanent glaciation in Antarctica began around 34 million years ago. However, it did not cover the entire continent as previously assumed, but was limited to the eastern part of the continent (East Antarctica). It was not until at least 7 million years later that the ice advanced to the West Antarctic coast.

The results of a new study show how differently East and West Antarctica respond to external influences, as researchers explain in a prestigious journal Science.

Beginning of Antarctic glaciation

About 34 million years ago, planet Earth experienced one of the most fundamental climatic changes that still affects global climate conditions today: the transition from a greenhouse world with little or no continental ice to a glaciated world with large, permanent glaciers. . region During this time, the Antarctic ice sheet was formed. How, when and above all where, is not yet known, due to the lack of reliable data and samples documenting past changes, especially from important regions such as West Antarctica.

Pioneering exploration of drill cores

Thanks to the core extracted by the MARUM-MeBo70 drilling rig near Pine Island in West Antarctica and the Thwaites glacier on the coast of the Amundsen Sea, it was possible to determine the date of the dawn of the Antarctic ice sheet for the first time on the continent. Surprisingly, no evidence of ice in this region can be found during the first major phase of Antarctic glaciation.

“This means that the first large-scale permanent glaciation must have started somewhere in East Antarctica,” says Dr. Johann Klages, a geologist at AWI who led the research team. “This is because West Antarctica was ice-free during this first glacial maximum. At that time, West Antarctica was still largely covered by dense broadleaf forests, and West Antarctica had a mild, cool climate that prevented ice formation.”

Different responses of East and West Antarctica

AWI paleoclimate modelers combined the newly available data with existing data on air and water temperatures and ice formation to better understand where the first permanent ice formed in Antarctica.

“The modelling confirmed the results of a unique geological core,” says AWI paleoclimate modeler Professor Dr. Gerrit Lohmann. “This completely changes what we know about the first Antarctic glaciation.”

According to the study, the main climatic conditions for the formation of permanent ice were only in the coastal areas of the Northern Victoria Region of East Antarctica. Here, moist air masses reached the powerfully rising Transantarctic Mountains – ideal conditions for the formation of permanent snow and subsequent ice sheets. From there, the ice sheet quickly spread into the interior of East Antarctica.

But it took some time to reach West Antarctica: “It wasn’t until seven million years later that conditions allowed the ice sheet to advance towards the West Antarctic coast,” explains AWI paleoclimate modeler Hanna Knal. “Our results clearly show how much the air had to cool before the ice could advance to cover West Antarctica, much of which was below sea level at the time.”

The research also shows how differently the two regions of the Antarctic ice sheet respond to external influences and fundamental climate change. “Even a small amount of warming is enough to re-melt the ice in West Antarctica, and that’s where we are now,” adds Johann Klages.

The findings of the international research team are critical to understanding the extreme climate transition from a greenhouse climate to our current glacial climate. Importantly, the research also provides new information that will allow climate models to more accurately simulate the impact of permanently glaciated areas on global climate dynamics, i.e. the interaction between ice, ocean and atmosphere. This is crucial, as Johann Klages says: “Especially in light of the fact that we could face such fundamental climate change again in the near future.”

Technological advances in Antarctic exploration

The researchers were able to fill this gap in knowledge with a unique core obtained during the PS104 expedition to the Polarstern research vessel in West Antarctica in 2017. The MARUM-MeBo70 drilling rig, developed at the Bremen-based MARUM facility, was used for the first time in Antarctica. The seabed near the Pine Island and Thwaites glaciers in West Antarctica is so hard that it was previously impossible to reach deep sediments using conventional drilling techniques. MARUM-MeBo70 has a rotating cutting head that makes it possible to drill about 10 meters into the seabed and extract samples.