Mapping Uncharted Waters

An autonomous underwater vehicle (AUV) called Autosub is about to become the first surveyor to breach one of the last unknown regions of the world. It will plunge into the unexplored pockets of the sea beneath the ice shelves of Antarctica. Travelling through the Amundsen Sea under the Pine Island Glacier ice shelf, Autosub will gather data for four projects sponsored by the Natural Environment Resource Council. The aim is to understand the interactions between the glacier and the ocean, which may reveal the effects of global warming on the Antarctic region.

Autosub is programmed to navigate through a cavity that runs for several hundred kilometres between the ice shelf and the sea floor. It will use simple logic software to get itself out of jams.Powered by 5,160 D-size batteries, the vehicle can run for 500 kilometres, covering this distance in roughly 3.5 days. It will measure water salinity, temperature and current, as well as mapping the sea floor and the bottom of the ice. It will also collect water samples for testing back in the lab.AUVs have gone under sea ice before in both the Arctic and the Antarctic. But this latest expedition is much riskier. Sea ice is usually only a few metres thick; in an emergency, a manned submarine or AUV could probably find a thin patch or hole to surface. Under an ice shelf, the only escape is to backtrack.

The Pine Island Glacier, one of the most dynamic and fast-moving Antarctic glaciers, sends more than 69 cubic kilometres of ice per year into the Amundsen Sea. In November 2001, an iceberg the size of New York City (some 714 square kilometres) broke off after a crack had spread across the glacier in 2000. Satellite data revealed thinning of the ice shelf during the 1990s. But the conditions and terrain are so treacherous that collecting data at the surface, even using tethered robotic vehicles, is too dangerous.