Fig. 1

Study area in the Ross Sea. Bottom topography (m) is shown in colour. The five study areas are indicated with rectangles: Terra Nova Bay (TNB), Drygalski Trough mouth (DT), Ross Island depression (RI), Joides Trough (JT) and Glomar Challenger Trough (GCT). See Supplementary Fig. 1 for the location of the oceanographic profiles used.