soil<\/a>; farther toward the open sea where it floats. Because climate change progressively warms the seawater, the latter is increasingly eroding the ice shelf from below.<\/p>\nThe grounding line, which is the last point at which the ice still rests on the ground, moves farther and farther inland. Due to meltwater and calving icebergs, the Thwaites Glacier, which flows into the Amundsen Sea, now loses twice as much ice as 30 years ago. If the West Antarctic Ice Sheet were to collapse entirely, global sea levels would rise by more than three metres.<\/p>\n
\u201cThe stability of the West Antarctic Ice Sheet is critical to the future development of the global sea level,\u201d explained Gabriele Uenzelmann-Neben lead author from the AWI. \u201cAccordingly, researchers around the world are working to predict the future behaviour of the ice in a warmer world using numerical simulation.<\/p>\n
\u201cThe 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 \u2013 particularly the formation phase. Our study delivers an important piece of the puzzle.\u201d<\/p>\n
How did researchers gather this novel information in this study?<\/h3>\n In the course of two research cruises on board the Polarstern, the Geophysicist and her team investigated sediments in the vicinity of Pine Island Trough, a channel-like furrow in the seafloor of the shallow part of the Amundsen Sea, which stretches from north to south and leads directly toward the western coast of Antarctica.<\/p>\n
To collect data, the AWI team relied on the tried and proven reflection seismology method: the Polarstern towed a 3,000-metre-long measuring cable behind her. The cable is equipped with hydrophones that utilise a total of 240 measuring channels. During survey cruises, an airgun is used to produce seismic pulses behind the ship.<\/p>\n
These pulses penetrate the seafloor and are reflected back at geological boundaries \u2013 between the sediment and hard rock, for example \u2013 which is recorded by the streamer\u2019s hydrophones. Based on the different travel times for the waves and the respective positions of the individual channels, the internal structure of the seafloor can be mapped by researchers.<\/p>\n
What did the research reveal?<\/h3>\n The measurement data revealed a large sediment body, a sediment drift, on the eastern flank of Pine Island Trough, one with no counterpart on its western side.<\/p>\n
Uenzelmann-Neben noted: \u201cBecause of the Coriolis effect produced by Earth\u2019s rotation, this asymmetrical deposition of a sediment drift on the trough\u2019s 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.<\/p>\n
\u201cIn order for that to occur, the ocean circulation at the time of the deposition had to be similar to today\u2019s 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.\u201d<\/p>\n
An additional study of pollen from the sediment cores gathered near the trough indicated that the base of the sediment drift was formed roughly 34- 36 million years ago. At precisely the same time \u2013 the Eocene-Oligocene boundary \u2013 temperatures plummeted around the globe, and the Antarctic continent became covered in ice.<\/p>\n
AWI geophysicists concluded: \u201cOur 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\u2019s expansion to the sea.<\/p>\n
\u201cThis important and unexpected finding emphasises 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\u2019s earliest phase, forecasts on its future stability and ice retreat can now be improved.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
A research team from the Alfred Wegner Institute, Helmholtz Centre for Polar and Marine Research (AWI), discovered that the formation of the West Antarctic ice sheet, up to 35 million years ago, may have been slower than previously believed. Roughly 35 million years ago, Earth cooled rapidly. At roughly the same time, the Drake Passage […]<\/p>\n","protected":false},"author":21,"featured_media":18620,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[24433,785],"tags":[700,745,689,789],"acf":[],"yoast_head":"\n
Delayed spread of Antarctic ice sheet revealed from 35 million years ago<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n \n \n \n \n \n\t \n\t \n\t \n