This dataset contains Autosub3 measurements (position, ice draft, sea bed depth, water temperature, salinity, depth and pressure) collected under the frame of the Natural Environment Research Council (NERC) Ice Sheet Stability Programme. The data were collected in the Amundsen Sea region of the Antarctic, more specifically in the Pine Island Glacier, during a series of missions from RRS James Clark Ross in February 2014. Radar measurements provided information about the bottom of the glacier, which then allowed for the definition of Autosub3 tracks for the different missions. Autosub3 was equipped with a CTD, oxygen sensor, transmissometer, GPS and ADCP. The Autosub missions were conducted as part of the ‘Ocean under ice: Ocean circulation and melting beneath the ice shelves of the south-eastern Amundsen Sea (iSTAR B)’ Project. This was one of four projects delivering the NERC Ice Sheet Stability Programme, aiming to better understand the physical processes governing the rate of ice melt in the West Antarctic ice sheet. The principal investigator for iSTAR B was Dr Adrian Jenkins from the British Antarctic Survey (BAS).