Scientists at the Scripps Institution of Oceanography in San Diego, US, recently showed science writers several of the latest designs for sampling tools capable of exploring water and sky while under the control of scientists who are miles away.
Scripps has pioneered three autonomous devices that have grabbed headlines in recent years. The first, called Argo, resembles a long diving tank and can rise and sink in the water column. It measures temperature, salinity and current, and sends its data via satellite. However, like a jellyfish, it can't propel itself and is slave to the currents. A similar device, an underwater glider called Spray, uses changes in buoyancy to create propulsion of about 1 kilometre per hour. This allows sampling over 3,000 kilometres of open ocean, but is not enough to travel against a strong current like the Gulf Stream.
Together, these devices have been leading a revolution in environmental sampling because they allow researchers to collect continuous data over hours, weeks or months. Since launching in 2000, the Argo programme has swelled to more than 3,200 floats across the world, though few exist under polar sea ice. Gliders are found in dozens of labs and in at least 10 different designs.
The data from these autonomous devices has focused the global climate picture as well as raising new questions.
"We knew that there was significant warming in oceans before Argo, but it is giving us a much better pattern of that warming," said Scripps' Dean Roemmich, a pioneer in underwater devices. "Specifically, the southern oceans are getting more heat than the rest – for reasons that have not been particularly well explained."
The creators of these tools say they are the most inexpensive way to sample data in out-of-the-way locations. Argo and Spray cost roughly $16,000 and $55,000 apiece, respectively.
The team's unmanned aerial vehicles (UAVs), meanwhile, are table-sized aeroplanes that can fly as high as 1,500 meters in tight formation, sampling the air between them. Unlike a satellite that looks at an entire column of air, UAVs can tease out specific regions of the sky. In 2007, they were instrumental for a paper in the journal Nature that measured the particulates in plumes, called brown clouds, over the Maldives. UAVs have been the slowest to catch on, being more expensive at $75,000, though with instrumentation the cost is more like $200,000. The UAVs are also difficult to share with foreign labs, since they contain US military technology and require high security clearance.
Although all three devices keep scientists out of harm's way, they are not without their own perils. A number of Argo floats have been attacked and even destroyed by curious sea creatures. Gliders run a substantial risk of being confused with torpedoes, just as UAVs resemble military drones; both are unpopular with foreign governments and limited in where they are allowed to deploy.
UAVs are also vulnerable, since they often fly at heights that are uncomfortably low for aeroplane pilots. Of the original six UAVs created at Scripps, only three remain. The rest were lost to what Hung Nguyen – associate director of C4, the Scripps programme that manages the drone – called "stupid mistakes". While this is certainly better than risking a human pilot, it makes one scientist nervous about installing equipment in the plane. "That is my biggest worry," says Richard Thomas, a C4 student who is designing an experiment using unmanned aeroplanes. "If I lose my equipment, I don't have another set. That's it."