Exploring beneath the PIG Ice Shelf with the Autosub3 AUV

On 31st January 2009, two numbers: “range and bearing” flashing up on a laptop screen, indicated that Autosub3 had returned from its last mission beneath the Pine Island Glacier (PIG) Ice Shelf in the Western Antarctic. The Autosub technical team from NOCS, Southampton, onboard the US ice breaker Nathanial B Palmer breathed a collective sigh of relief. Any significant technical failure would have resulted in total loss of the multi million Euro Autonomous Underwater Vehicle with no hope of recovery from 60 km into the ice shelf cavity. This was the last of six successful missions to investigate the shape the ice shelf, the sea bed bathymetry, the currents and the physical oceanography within the ice cavity. Each are vital to understanding the interaction between the sea water and the ice shelf, and quantifying whether the melting rate is changing. During the cruise, Autosub3 had run beneath the ice for almost 4 days and for 510 km.