The analysis of seismic reflection data from the Amundsen Sea, southern Pacific Ocean reveals sediment drift formation already in Eocene/Oligocene times. This observation indicates bottom current activity and hence a cold climate for the late Paleogene in an area, which today lies under the influence of AABW originating in the Ross Sea. The creation of sediment drifts increased accompanied by the occurrence of debris flows leading to the identification of a phase of strong ice sheet extension, which then was followed by retreat of the grounding line during the last 9 Ma.