“Important and Unexpected Finding”– Formation of the West Antarctic Ice Sheet Was Very Different Than Previously Believed

AWI professionals verify the postponed spread of the ice sheet 35 million years earlier.

Roughly 35 million years earlier, Earth cooled quickly. At approximately the exact same time, the Drake Passage formed in between South America and the Antarctic, leading the way for the Antarctic CircumpolarCurrent Thanks to these 2 aspects, Antarctica was quickly entirely covered in ice. As a research study from the Alfred Wegener Institute now reveals, this huge glaciation was postponed in a minimum of one area. This brand-new piece of the puzzle worrying the early history of the West Antarctic Ice Sheet might assist to forecast its unsteady future. The research study was simply launched in the Nature journal Communications Earth & &Environment

For environment scientists, the West Antarctic has actually remained in the spotlight for many years. Here, the West Antarctic Ice Sheet lying atop the continent extends to the nearby AmundsenSea Near the coast, the ice is still in direct contact with the soil; further towards the ocean blue, it drifts. Because environment modification gradually warms the seawater, the latter is significantly wearing down the ice rack from listed below. The grounding line– the last point at which the ice still rests on the ground– moves further and further inland. Due to meltwater and calving icebergs, the Thwaites Glacier, which streams into the Amundsen Sea, now loses two times as much ice as 30 years earlier. If the West Antarctic Ice Sheet were to collapse totally, worldwide water level would increase by more than 3 meters.

“The stability of the West Antarctic Ice Sheet is critical to the future development of the global sea level,” states the research study’s very first author, Gabriele Uenzelmann-Neben from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). “Accordingly, researchers around the world are working to predict the future behavior of the ice in a warmer world using numerical simulation. The more we know about the history of the West Antarctic Ice Sheet, the more accurate we can make these models. Its more recent history is well-documented, but we still know very little about its earlier years – particularly the formation phase. Our study delivers an important piece of the puzzle.”

In the course of 2 research study cruises onboard the Polarstern, the Geophysicist and her group examined sediments in the area of Pine Island Trough, a channel-like furrow in the seafloor of the shallow part of the Amundsen Sea that extends from north to south and leads straight towards the western coast ofAntarctica To gather information, the AWI group depended on the attempted and shown reflection seismology technique: the Polarstern hauled a 3,000- meter-long determining cable television– or banner– behind her. The banner is geared up with hydrophones that make use of an overall of 240 measuring channels. During study cruises, an airgun is utilized to produce seismic pulses behind the ship. These pulses permeate the seafloor and are shown back at geological borders– e.g. in between the sediment and acid rock– which is taped by the banner’s hydrophones. Based on the various travel times for the waves and the particular positions of the private channels, the internal structure of the seafloor can be mapped.

The measurement information exposed a big sediment body, a sediment drift, on the eastern flank of Pine Island Trough, one without any equivalent on its western side. “Because of the Coriolis effect produced by Earth’s rotation, this asymmetrical deposition of a sediment drift on the trough’s eastern side but not the western one can only have been produced by a deep-water current that flowed toward the coast from north to south,” states Uenzelmann-Neben “In order for that to occur, the ocean circulation at the time of the deposition had to be similar to today’s conditions, that is, the prevailing westerlies and the Antarctic Circumpolar Current had to have been located far to the south. And similar to today, the deep water upwelled through the trough must have been comparatively warm.”

Additional research study of pollen from sediment cores collected near the trough suggest that the base of the sediment drift was formed approximately 34 to 36 million years earlier. At specifically the exact same time– the Eocene-Oligocene border– temperature levels dropped around the world, and the Antarctic continent ended up being covered in ice. “Our study offers compelling evidence that at the time of the great glaciation, warmer deep water upwelled near the Amundsen Sea shelf and delayed the West Antarctic Ice Sheet’s expansion to the sea,” the AWI Geophysicist describes. “This important and unexpected finding emphasizes the tremendous importance that ocean currents had even during the formation phase of the West Antarctic Ice Sheet and continue to have today. Armed with this additional knowledge concerning the ice sheet’s earliest phase, forecasts on its future stability and ice retreat can now be improved.”

Reference: “Deep water inflow slowed offshore expansion of the West Antarctic Ice Sheet at the Eocene-Oligocene transition” by Gabriele Uenzelmann-Neben, Karsten Gohl, Katharina Hochmuth, Ulrich Salzmann, Robert D. Larter, Claus-Dieter Hillenbrand, Johann P. Klages and Science Team of Expedition PS104, 21 February 2022, Communications Earth & & Environment
DOI: 10.1038/ s43247-022-00369- x