Record drilling under Ross Ice Shelf: longest sediment core offers new clues to West Antarctic Ice Sheet future
An international team of researchers has drilled the longest sediment core (228 m) to date under the Ross Ice Shelf in West Antarctica – some 700 kilometers away from the nearest research station. The samples obtained will provide insights into times when the West Antarctic Ice Sheet melted during the last 23 million years, covering periods when the Earth was warmer and richer in CO₂ than it is today. The West Antarctic Ice Sheet contains enough ice to raise global sea levels by up to five meters. Several German institutes are involved in the SWAIS2C project, and a German scientist was present during the drilling in the field.
Satellite observations over the last few decades show that the West Antarctic Ice Sheet is losing mass at an accelerating rate. The ice sheet is supported on one side by the Ross Ice Shelf – the largest floating ice mass on Earth. This buttresses the ice and slows down the flow of glaciers and ice streams towards the ocean. However, it is still unclear how much more the Earth can warm before unstoppable melting of the ice shelf occurs, thus triggering the loss of the West Antarctic Ice Sheet.
Geological drilling mission directly at the transition between the Ross Ice Shelf and the West Antarctic Ice Sheet
Until now, researchers have based their model calculations of the ice sheet's development on geological data collected either near the ice sheet, under floating shelf or sea ice, in the open Ross Sea, or in the Southern Ocean. The new sediment record was obtained as part of the SWAIS2C project (Sensitivity of the West Antarctic Ice Sheet to 2°C of Warming) under a 523-meter-thick layer of ice at the so-called Crary Ice Rise, directly at the edge of the Ross Ice Shelf's transition zone to the West Antarctic Ice Sheet.
“These records will provide us with important insights into how the West Antarctic Ice Sheet and the Ross Ice Shelf will respond to temperatures above 2°C. Initial indications suggest that the sediment layers span approximately the last 23 million years, including periods when global average temperatures were significantly above 2°C compared to pre-industrial levels,” says Dr Huw Horgan, SWAIS2C co-chief scientist from Victoria University of Wellington (New Zealand), ETH Zürich and WSL (Switzerland).
“We are thrilled to have finally obtained such a record core, which will reveal how the West Antarctic Ice Sheet in the Ross Sea sector reacted during periods that were warmer and richer in CO₂ than today,” adds Dr Johann Klages, German co-coordinator of the SWAIS2C project and geoscientist at the Alfred Wegener Institute. "Together with drill cores that we plan to obtain next year with the research vessel Polarstern and the seafloor drill rig MeBo in the Amundsen Sea, these new and extremely difficult-to-obtain archives will hopefully enable us to answer the question of when and under what conditions the West Antarctic Ice Sheet will disappear – key data for testing and fundamentally improving the reliability of the latest climate and ice sheet models.“
Dr Andreas Läufer, German coordinator of the SWAIS2C project and geologist at the Federal Institute for Geosciences and Natural Resources, adds, “We have far exceeded our goal of 200 m, and that's 700 km away from the nearest base – that's pioneering Antarctic science.”
Major logistical and technical challenges for the research mission
The “on-ice” team of 29 people, including Dr Arne Ulfers from the LIAG Institute for Applied Geophysics in Hanover, Germany, lived in tents on the ice for almost ten weeks. Beforehand, the specially developed drilling system and field equipment had to be transported 1,100 km across the Ross Ice Shelf with PistenBullys. The weather also posed a major challenge, as flights for the drilling team and researchers to the camp were delayed by weeks due to ice fog at the camp.
In order to access the hard-to-reach sediment, the project team first had to melt a hole through the 523-meter-thick ice using hot water. The core segments were then pulled out meter by meter. The researchers described, photographed, and X-rayed the sections and took initial samples. Finally, measurements were taken in the borehole itself. The team worked around the clock in shifts.
“Conducting research under such extreme Antarctic conditions and at the limits of what is technically feasible is a particular challenge. It is therefore all the more gratifying that we have succeeded and that this important sediment archive can now be analyzed,” explains Dr Arne Ulfers. “The Intergovernmental Panel on Climate Change (IPCC) has predicted various climate scenarios for the coming century. This makes it all the more crucial that we continue to dedicate ourselves to the global task of complying with the Paris Climate Agreement and limiting global warming to 2 degrees Celsius or less.”
Evidence of open ocean conditions indicates melted ice shelf
During their investigations, the researchers encountered a variety of different sediment types, ranging from fine-grained sediment to more massive material with large rocks embedded in it. Preliminary on-site dating of the sediment was based on the identification of tiny fossils of marine organisms found in some of the layers.
The presence of shell fragments and remains of marine organisms that require light to survive indicates open ocean conditions. “This new record confirms the assumption that there was an ice-free ocean in this region in the past. Further analysis of the drilled record will help us determine when this happened and how long it lasted, as well as what conditions led to the melting of the ice,” says co-chief scientist Dr Molly Patterson of Binghamton University (United States).
Next steps: Analysis of sediments around the world
The core was first transported to the New Zealand Scott Research Base before continuing its journey to New Zealand. “The initial preliminary evidence that there were ice-free phases in the past is extremely exciting and scientifically promising. Extensive further research is now needed to understand the climatic conditions under which these were formed,” explains Professor Dr Denise Kulhanek from Kiel University (CAU) and member of the SWAIS2C scientific management team. “We are currently planning a core description workshop in June, where we will open the sediment cores and describe them in detail together with a core team of SWAIS2C researchers. This work is crucial for narrowing down the timeframe and duration of earlier ice-free phases more precisely,” Kulhanek continues. Samples will then be distributed to participating SWAIS2C scientists worldwide for further analysis.
Background
The SWAIS2C project is a collaboration among researchers from ten countries – New Zealand, USA, Germany, Australia, Italy, Japan, Spain, Korea, Netherlands, and United Kingdom – with more than 120 scientists. It is led by Dr Molly Patterson (Binghamton University, United States), Dr Huw Horgan (Te Herenga Waka – Victoria University of Wellington, New Zealand, ETH Zurich and WSL, Switzerland), Professor Dr Tina van de Flierdt (Imperial College London), and Professor Dr Richard Levy (Earth Sciences New Zealand and Te Herenga Waka – Victoria University of Wellington, New Zealand). Researchers from Germany are involved from the Federal Institute for Geosciences and Natural Resources (BGR, Hanover), the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI, Bremerhaven), the LIAG Institute for Applied Geophysics (LIAG, Hanover), and Kiel University (CAU, Kiel).
Wissenschaftlicher Ansprechpartner:
Federal Institute for Geosciences and Natural Resources (BGR)
Polar Geology
Dr Andreas Läufer
Phone: +49 511 643 3137
Email: Andreas.Laeufer@bgr.de
Kiel University (CAU)
Institute of Geosciences
Professor Dr Denise Kulhanek
Phone: +49 (0)431 880 2924
Email: Denise.Kulhanek@ifg.uni-kiel.de
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research
Section Marine Geology
Dr Johann P. Klages
Phone: +49 (0)471 4831 1216
Email: Johann.Klages@awi.de
LIAG Institute for Applied Geophysics
Dr Arne Ulfers
Phone: +49 (0)511 643 2577
Email: Arne.Ulfers@liag-institut.de
Weitere Informationen:
https://swais2c.aq/
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