Obtaining unique geological samples sheds light on the formation of today’s Antarctic ice sheet

In recent years, global warming has taken its toll on the Antarctic ice sheets. Antarctica’s “eternal” ice is melting faster than previously thought, especially in West Antarctica more than in East Antarctica. The root of this could lie in its origin, as an international research team led by the Alfred Wegener Institute has now discovered.

Sediment samples from drill cores combined with comprehensive climate and ice sheet modeling show that permanent glaciation of Antarctica began about 34 million years ago – but did not involve the entire continent as previously thought, but rather was limited to the eastern region of the continent (East Antarctica). It was not until 7 million years later that the ice was able to advance towards the west Antarctic coast.

The results of the new study show how East and West Antarctica react significantly differently to external influences, as the scientists describe in the journal. Science.

About 34 million years ago, our planet underwent one of the most fundamental climate changes that still affects global climate conditions today: the transition from a greenhouse world (with no or very little accumulation of continental ice) to a glacier world (with large permanently glaciated areas). areas). During this time, the Antarctic ice sheet formed. How, when, and especially where were not yet known due to a lack of reliable data and samples from key areas, particularly West Antarctica, that documented changes in the past.

Researchers from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI), together with colleagues from the British Antarctic Survey, Heidelberg University, Northumbria University (UK) and MARUM – Center have now managed to fill this knowledge gap. for Marine Environmental Sciences at the University of Bremen, in addition to collaborators from the universities of Aachen, Leipzig, Hamburg, Bremen and Kiel as well as the University of Tasmania (Australia), Imperial College London (UK), Université de Fribourg (Switzerland), Universidad de Granada (Spain), Leicester University (UK), Texas A&M University (USA), Senckenberg am Meer and the Federal Institute for Geosciences and Natural Resources in Hannover, Germany.

Based on a drill core obtained by the MARUM-MeBo70 seabed drilling rig at a location off the coast of the Pine Island and Thwaites glaciers on the coast of the Amundsen Sea in West Antarctica, scientists were able to determine the dawn history of the Antarctic ice sheet. continent for the first time. Surprisingly, no signs of ice can be found in this area 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 from the AWI who led the research team. This is because West Antarctica remained ice-free during this first glacial maximum. At the time, it was still largely covered by dense deciduous forests and a cold temperate climate that prevented the formation of ice in West Antarctica.

East and West Antarctica react very differently to external conditions

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

“The simulation supported the results of a unique core of geologists,” says Professor Dr. Gerrit Lohmann, paleoclimate modeler at AWI. “This completely changes what we know about the first glaciation of Antarctica.”

According to the study, the basic climatic conditions for the formation of permanent ice prevailed only in the coastal areas of eastern Antarctica, Northern Victoria Land. Here, masses of moist air entered the strongly rising Transantarctic Mountains — ideal conditions for permanent snowfall and the subsequent formation of ice caps. From there, the ice sheet spread rapidly into the interior of East Antarctica. However, it took some time to reach West Antarctica.

“It wasn’t until about seven million years later that conditions allowed the ice sheet to advance to the West Antarctic coast,” explains Hanna Knahl, paleoclimate modeler at AWI. “Our results clearly show how cold it had to cool before the ice could advance and cover West Antarctica, which was already below sea level in many places at the time.”

The research also impressively shows how the two regions of the Antarctic ice sheet react differently to external influences and major climate changes.

“Even mild warming is enough to melt the ice in West Antarctica again – and that’s exactly where we are right now,” adds Klages.

The international research team’s findings are critical to understanding the extreme climate transition from a greenhouse climate to our current glacial climate. Importantly, the study also provides new insight that allows climate models to more accurately simulate how permanently glaciated areas affect global climate dynamics, i.e. the interactions between ice, ocean and atmosphere.

This is of critical importance, Klages says, “especially in light of the fact that we could again face such major climate change in the near future.”

Using new technology, you will gain unique insights

Scientists managed to close this gap in knowledge using a unique drill core obtained during the PS104 expedition on the Polarstern research vessel in West Antarctica in 2017. The MARUM-MeBo70 drilling rig developed at MARUM in Bremen was used for the first time in Antarctica.

The seabed at the West Antarctic Pine Island and Thwaites glaciers is so hard that it was previously impossible to reach deep sediments using conventional drilling methods. The MARUM-MeBo70 has a rotary cutting head that allowed it to drill about 10 meters into the seabed and retrieve samples.