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. A researcher works on Deep SOLO, part of the Deep Argo program. Image: Scripps Institution of Oceanography, UC San Diego.