Site: Palmer Antarctica LTER
Rutgers-Slocum glider surfacing near the research vessel Laurence M Gould near Palmer Antarctica LTER.

The observed changes in polar ecosystems require the research community to develop the capacity to resolve changes and understand their global implications. Traditional modes of sampling will not suffice and efforts must be focused on developing networks capable of operating in a harsh environment and maintaining themselves for sustained periods at sea. Realizing this, PAL scientists have developed the first sustained underwater polar robotic network to overcome the chronic undersampling of the Antarctic Peninsula region. The network is modular and its success has resulted in similar technologies being deployed throughout Antarctica in 2011.

The PAL autonomous underwater vehicle (AUV) network consists of a fleet of underwater Slocum buoyancy gliders. Slocum gliders are 1.8 m long torpedo-shaped, winged AUVs that maneuver through the ocean at a forward speed of 20-30 cm/s in a sawtooth-shaped gliding trajectory, deriving their forward propulsion by means of a buoyancy change and steering with a tail fin rudder. An altimeter and depth sensor enable preprogrammed sampling of the full water column. The primary vehicle navigation system uses an on-board GPS receiver coupled with an attitude sensor, depth sensor, and altimeter to provide dead-reckoned navigation. Global communications provided by Iridium allow the robots to be controlled from laboratories in Antarctica or New Jersey. Glider operations are anchored by technicians and advanced undergraduates on campus at Rutgers University. Students learn oceanography while supporting the PAL field research teams by processing the real-time data and delivering back to the field researchers to enable adaptive sampling.

The gliders are outfitted with a variety of sensors measuring physics, chemistry, optics and acoustics allowing scientists to study ecosystem processes spanning from phytoplankton dynamics to penguin foraging ecology. Since the initial deployment in 2007, PAL gliders have flown 20 missions mapping 3076 kilometers underwater over 171 days. The success of the PAL gliders provide a model for polar robotic networks and the experience gained was central to successful first-time glider deployments in the Amudsen and Ross Seas. In 2009, a PAL glider was successfully flown several hundred km from an American research vessel to the British Antarctic Base Rothera, the first joint international glider effort. That success motivated the British to purchase 2 gliders, which will be operated in partnership with PAL to form the first regional polar robotic network in the world.

This evolving regional network will allow the LTER to sample the WAP throughout the year and will provide a technology test bed for polar technologies. This was demonstrated at Palmer station in 2011 when gliders were combined with propeller AUVs were coordinated using real-time satellite-telemetry data collected by penguins.

The data allowed the penguin location and depth of foraging to design sampling missions by the robots. A nested sampling used gliders to map the mesoscale dynamics and the propeller AUVs collected highly resolved maps at the specific locations and depths where penguins were foraging. This was the first time a robotic network had been coordinated by real-time animal data and provides a template for future networks being designed to resolve ecological dynamics in natural populations.

Graph for
Cruise track for glider flight from Palmer Station (north) to Rothera Base (south) in January, 2009. The color contours show the north to south (about 500 km) and vertical (0 to 100 meters depth) distribution of chlorophyll fluorescence, an indicator of the amount pf phytoplankton in the water.