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. “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,” says 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 study of pollen from sediment cores gathered near the trough indicate that the base of the sediment drift was formed roughly 34 to 36 million years ago. At precisely the same time – the Eocene-Oligocene boundary – temperatures plummeted around the globe, and the Antarctic continent became 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 explains. “This 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’s earliest phase, forecasts on its future stability and ice retreat can now be improved.”
ATTENTION: Dr Uenzelmann-Neben is currently on expedition and can only be reached by e-mail.