Of all the environments on our planet, the deep ocean is still pretty much unknown. Scientists like to say that we've mapped more of the Moon than we have of our ocean floor. But there's a growing need to monitor the ocean's abyss, which is warming in response to climate change, just like everywhere else, creating consequences we can't fully predict.
On Tuesday, a meeting of scientists from around the world—including Canada, the US, and France—kicked off in Yokohama, Japan to discuss Argo, a global array of roughly 3,000 free-floating ocean probes that measure changes in temperature and salinity. These battery-powered devices can dip down 2,000 meters (1.25 miles), and versions of them have been drifting through the oceans for over a decade, gathering data.
Now, scientists hope to deploy a heftier version of the probe, Deep Argo, that could reach an astonishing 6,000m down. That's over 19,600 feet, a place so inhospitable—there's few nutrients, extreme pressure, and no sunlight that deep—that not many creatures can survive there. With enough Deep Argos moving through the water, scientists would have a way to monitor places they've never really managed to reach.
Before Argo, the best thing oceanographers had to go on was surveys done by ship, said Denis Gilbert, the past director of Argo Canada, who's based at the Institut Maurice-Lamontagne in Mont-Joli, Quebec. But those aren't repeated often enough to be very useful. (Another creative scheme involved gluing satellite tags onto elephant seals, to pick up data about ocean conditions while they swim.)
"Argo has changed the standards of global monitoring for the oceans," Gilbert said. In the southern hemisphere, floats collect more data—every single year—than what was gathered in over six decades of oceanography, before the program came into being.
Argo floats help scientists learn about ocean currents, too, because they travel by riding them, Gregory Johnson, a Seattle-based oceanographer with the National Oceanographic and Atmospheric Administration, told me. According to him, floats sink to a depth of 1,000m, then drift along for nearly two weeks before lowering to 2,000m, and come back up. "As they rise, they collect data on temperature, salinity, and pressure," he said. "They surface and phone home," transmitting data back to centers in Monterey, Calif. and Brest, France. Within 24 hours of transmission, the data is ready for anyone to use.
As our planet warms up, our oceans act like a giant heat sponge
Unlike the Argo floats, which are aluminum and cylinder-shaped, Deep Argo prototypes are glass spheres designed to withstand the deep ocean's crushing pressures. Johnson calls the glass sphere a "venerable oceanographic flotation device," stuffed full of scientific instruments. A few have already been deployed, but scientists like Johnson hope to see many more. "We'd need about 1,200 globally," he estimated. According to a report in Nature, the NOAA is spending about $1 million annually to get Deep Argo off the ground.
With a network of robotic Deep Argo probes diving down to 6,000m, scientists will be able to measure "almost 99 per cent of the ocean volume," Johnson said—basically everything short of what's inside the deepest ocean trenches. (The deepest point on Earth, at the bottom of the Mariana Trench, is over 10,000m below the surface.)
Once the meeting in Yokohama wraps up, on Thursday, we can hope they'll be more news about Deep Argo. It's critical. As our planet warms up, our oceans act like a giant sponge, absorbing more than 90 per cent of the excess heat, according to the Intergovernmental Panel on Climate Change. What happens in the deep ocean, still the most mysterious and little-understood of all environments, will affect us deeply.