Slocum Electric Gliders

Electric and Thermal Gliders Join Alace Floats Monitoring Oceans

Jan 30, 2009 John Blatchford

Several autonomous robots are now wandering the oceans gathering data.

In the past the only way to get information about distant seas was to go there by boat and throw equipment overboard. This made observations very expensive, and often ruled out the possibility of working during periods of bad weather. New equipment is changing all this.

Slocum Autonomous Underwater Gliding Vehicles

• The first of these AUGVs was the ‘Slocum Electric Glider’, first suggested by Henry Stommel (a famous physical oceanographer) back in 1989. They were eventually built by Doug Webb in 2005 and some are now cruising the oceans. They were named after Joshua Slocum, who the first man to sail around the world on his own.

• These ‘Electric Gliders’ use battery power to alter their buoyancy periodically, so they can rise to the surface to transmit their findings via a satellite before submerging once more to their prescribed depth to drift around and get more data. They have remotely adjustable wings and fins so that their routes can be planned to some extent.

• Much of their horizontal movement is determined by the relative directions of the surface and deep-water currents, and much like plankton, simply going up and down gives them lateral motion.

• Battery life is used up altering buoyancy with each dive, and this limits the length of time they can operate between re-charges to about 100 days.

• A new generation of Slocum Gliders is currently being tested – one which uses the vertical temperature gradients in the sea to alter buoyancy automatically at pre-determined depths. These are the ‘Slocum Thermal Gliders’, and since they use much less power they can stay at sea for a number of years (about 5 years, covering around 40,000 km).

Monitoring Equipment

• The first things being measured are water temperature and salinity, but there are plans to add other sensors and measure additional things like turbidity (how many particles there are in the water), and even chlorophyll levels (to assess how much photosynthesis is going on).

• Naturally the periodic re-surfacing from the depths will also give some information about ocean currents, and this will add to the data being sent in from the ‘Argo’ project (where 3,000 ‘Alace’ floats are already deployed around the world gathering information about the deeper currents). Read more about ‘Project Argo’.

The data that is being collected by all these robots will give us huge amounts of information about the oceans, and it is hoped that ever more accurate computer modelling will be possible. In the future it should lead to much more accurate weather prediction, as well as improving our understanding of ocean systems.

Main reference: New Scientist, 29 November 2008

The copyright of the article Slocum Electric Gliders in Marine Biology & Oceanography is owned by John Blatchford. Permission to republish Slocum Electric Gliders in print or online must be granted by the author in writing.

Slocum Autonomous Underwater Gliding Vehicle

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