Deep-Sea Drone Floats Could Sample 98 Percent of Ocean Volume by 2028

The Argo Program is an international collaboration launched in 1999 that deploys 4,000 data-collection floats worldwide. Most of those floats descend between 2,000 and 4,000 meters, while 10 percent of ocean warming occurs below that range, leaving a gap in data collection. The two Deep-6000 prototypes completed their five 6,000-meter dives between January 11 and February 2, collecting data on the abyssal zone. The United States currently operates more than 100 deep-sea floats and China more than 30.

More than 90 percent of the ocean is considered deep ocean, reaching 200 meters (656 feet) or more, and only 5 percent of the entire ocean has been explored. The obstacle is largely technical: the ocean adds roughly one atmosphere of pressure for every 10 meters of depth, so at 6,000 meters the pressure is about 600 times that at sea level. "The main challenge was to design a system that could withstand the pressures of the deep sea, be self-sufficient in terms of energy to remain operational for seven years, and keep costs under control," Xavier André, head of profiler technology development at Ifremer, said in a press release.

To cope with that pressure, Ifremer built the hulls of its Deep-6000 prototypes from composite materials rather than pure titanium. At 88 pounds, the devices weigh about twice as much as a typical Argo float. The floats run on ten-day cycles: dropped from a boat, a float descends to a drift depth and stays there for nine days, then goes deeper to a profile depth for about three hours, and finally rises to the surface to send its data to a satellite. The process repeats until the battery dies, usually around 150 cycles over three to five years.

The floats measure water salinity, temperature, oxygen and pressure, information that weather and climate centers use to track how the ocean behaves as climate change warms the water. Argo data can improve forecasts of monsoons, ocean warming, sea-level rise and ocean circulation. The 4,000 floats now in service produce more than 100,000 temperature and salinity profiles a year, and all Argo data is free to access online.

Virginie Thierry, a physical oceanographer at Ifremer, said in a press release that the new Deep-6000 floats will let the organization track ocean warming through abyssal depths. "We will also be able to obtain information on deep ocean circulation, which contributes to the storage of climate signals such as heat and carbon in the deep ocean, and refine ocean prediction models," she said. "Argo is an example of truly remarkable international cooperation, with more than 60 countries contributing to it."