Ice Planet Update: A Droid Lands on Antarctic Ocean – Formation of Antarctica’s Ice Sheet

In recent years, global warming has left its mark on the Antarctic ice sheets. „Eternal” ice in Antarctica is melting faster than previously thought, especially in West Antarctica more than in East Antarctica.

As an international research team led by the Alfred Wegener Institute has now discovered, the root of this lies in its formation: Sediment samples from drill cores combined with complex climate and ice-sheet modeling show that Antarctica’s permafrost began around 34 million years ago. Previously – but not covering the entire continent as previously thought, but only the eastern part of the continent (East Antarctica).

It was only after at least 7 million years that the ice sheet was able to advance towards the West Antarctic coast. The results of the new study show how differently East and West Antarctica respond to external forcing, the researchers describe in the prestigious 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 continental ice sheets or very little accumulation, to an icehouse world, a world permanently covered with glaciers. areas. During this time, the Antarctic ice sheet built up. Lacking reliable data and models from key regions documenting past changes, particularly from West Antarctica, how, when and, where, are not yet known.

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 the MARUM – Center have now managed to close this knowledge gap. for Marine Environmental Science at the University of Bremen, with collaborators from the Universities of Aachen, Leipzig, Hamburg, Bremen and Kiel, University of Tasmania (Australia), Imperial College London (UK), Universität de Friborg (Switzerland), Universitat de Granada (Spain), University of Leicester (UK) , Texas A&M University (USA), Senckenberg am Meer and Federal Institute for Geosciences and Natural Resources in Hannover, Germany.

RV Polarstern in Inner Pine Island Bay – Photo: R. Larder, BAS

Based on a drill core recovered by researchers using the MARUM-MeBo70 seabed drilling rig off the Pine Island and Thwaites glaciers off the coast of West Antarctica’s Amundsen Sea, they were able to establish the history of the dawn of icy Antarctica. Continent for the first time. Surprisingly, no signs of ice were found in this area during the first major phase of Antarctic glaciation. „This means that a large-scale, permanent first glaciation must have started somewhere in East Antarctica,” says Dr Johan Klages, a geologist at AWI who led the research team. Because West Antarctica was ice-free during this first glacial maximum. At this time, it was still mostly covered with dense broadleaf forest and the cold-temperate climate prevented ice from forming 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 newly available data with existing data on air and water temperatures and ice sheet events. „The simulations have supported the results of a unique focus of geologists,” says Professor Dr. Gerrit Lohmann, paleoclimate modeler at AWI.

„This completely changes what we know about the first Antarctic glaciation.” According to the study, the basic climatic conditions for the formation of permafrost existed only in the coastal areas of the East Antarctic Northern Victoria Land. Here, moist air masses reached the strongly rising Transantarctic Mountains – conditions ideal for the formation of permafrost and subsequent ice sheets. From there, the ice quickly spread into the East Antarctic interior.

However, it took a while for it to reach West Antarctica: „It was only seven million years later that an ice sheet was allowed to advance to the West Antarctic coast,” explains Hannah Knall, AWI’s paleoclimate modeller. „At that time, our results clearly show how cold it was before the ice sheet advanced to cover West Antarctica, which was already below sea level in many areas.” Studies have shown interestingly how the two regions of the Antarctic ice sheet respond to external influences and fundamental climate changes. „Even a small amount of warming is enough to melt the ice in West Antarctica again – and that’s what we’re in now,” says Johan Klages.

The international research team’s findings are critical to understanding the extreme climate change from a greenhouse climate to our current icehouse climate. Importantly, the study also provides new insight that will allow climate models to more accurately simulate how glaciated areas permanently affect global climate dynamics—interactions between ice, ocean, and atmosphere. This is especially important, as Johan Klages says: „Especially in light of the fact that we could face such a fundamental climate change again in the future.”

Using new technology to gain unique insights

Researchers were able to close this knowledge gap with the help of a unique drill core recovered in 2017 during the research vessel PS104 in West Antarctica on the research vessel Polarstern. A MARUM-MeBo70 drill rig developed at MARUM in Bremen was used. First time in Antarctica. The seabed beyond the West Antarctic Pine Island and the Thwaites Glaciers is so difficult that deep sediments cannot be reached using conventional drilling methods. The MARUM-MeBo70 has a rotating cutterhead that was able to drill down to about 10 meters of seabed and retrieve samples.

The research project, and in particular Polarstern Expedition PS104, was funded by AWI, MARUM, the British Antarctic Survey and the NERC UK-IODP programme.

Original publication

JP Glaze, C.-D. Hillenbrand, SM Bohaty, U. Salzmann, T. Bickert, G. Lohmann, HS Knahl, P. Gierz, L. Niu, J. Titschack, G. Kuhn, T. Frederics, J. Muller, T. Bauersachs, RD Larter. , K. Hochmuth, W. Erman, G. Nehrke, F.J. Rodriguez-Dover, G. Schmidt, S. Spezzaferri, A. Luffer, F. Lisker, D. Van de Filyard, A. Eisenhower, G. Yunselman-Neban, O. Esper, JA Smith, H. Pälike, C. Spiegel, R. Dziadek, TA Ronge, T. Freudenthal and K. Gohl. Ice-free West Antarctica during the early Oligocene glaciation. (2024) DOI: 10.1126/science.adj3931.

Astronomy