Editor’s note: As we plan to use robotic probes such as Saildrone to explore worlds in our solar system with oceans, missions that explore Earth’s oceans can serve as important pathfinders. See also: Saildrone Surveyor Away Team Completes Uncrewed Alaska Ocean Mapping Mission
[NOAA] The Southern Ocean is one of the roughest and most dangerous bodies of water on Earth. It’s also key to understanding the global climate system.
The vast distances and harsh conditions of the Southern Ocean have discouraged traditional ship-borne investigations that would help researchers resolve significant questions about just how much carbon dioxide (CO2) the ocean absorbs, especially in winter. That’s why scientists are now turning to uncrewed systems.
On September 19, 2026, the first of four sturdy, instrumented Saildrone Explorer uncrewed surface vehicles (USVs) departed from Hobart, Tasmania, marking the start of an ambitious, five-year effort to tackle this challenge.
Led by researchers at NOAA, Columbia University, Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO), the Constraining Ocean Carbon with Optimized Observing (COCO2) project will deploy three more Saildrones every three months during 2027. The small fleet will repeatedly circumnavigate Antarctica, collecting data about the ocean around them as they navigate along courses identified by AI-driven ocean-air models to intersect with high-value target areas.
The ocean stores about a third of CO2 absorbed from the atmosphere each year, and scientists estimate the Southern Ocean accounts for 40% of the total, said Adrienne Sutton, an oceanographer at NOAA’s Pacific Marine Environmental Laboratory and a co-lead of the project.
“The global ocean is Earth’s largest carbon sink, and the Southern Ocean plays an outsized role,” Sutton said. “With COCO2 we are filling a critical knowledge gap by adding observations during winter — something we have not been able to do with traditional oceanographic tools.”
Revolutionizing ocean science
Saildrones are remotely controlled mobile research platforms propelled by the wind, with solar-powered onboard systems that enable them to operate for long periods in distant waters while transmitting data in near-real time.
Instruments fitted to each Saildrone will make continuous, direct measurements of CO2 being exchanged between the air and ocean — along with wind speed and direction, barometric pressure, solar radiation, relative humidity, air temperature, sea surface temperature, salinity, chlorophyll and dissolved oxygen. As each Saildrone completes a roughly 12,000-mile circumnavigation of Antarctica, it will return to port for repairs and refurbishment before being redeployed for another voyage around the South Pole.
The data collected will help scientists develop more confident estimates of CO2 absorption, while gaining insights to one of Earth’s most inhospitable environments. Data from the drones are delivered to PMEL where automated processes route it to research users and the World Meteorological Organization’s Global Telecommunication System (GTS) for use with global weather models.
A map of Earth showing Antarctica labeled with a likely path (in red) that a Saildrone uncrewed system might take around Antarctica for the 2026 COCO2 5-year mission.
An example of the kind of route (labeled in red) Saildrones will navigate as they sail around Antarctica during the 2026 COCO2 five-year mission. (Image credit: Saildrone, Inc.)
An outsized influence over the global climate
What sets the Southern Ocean apart is that it’s confined not by continents, but by a current — the Antarctic Circumpolar Current — an invisible boundary whose constant motion drives a massive exchange of heat and carbon between the atmosphere and ocean depths.
For years, scientists assumed that the Southern Ocean steadily absorbed large volumes of CO2, although they knew shifts in winds and circulation around Antarctica could alter CO2 uptake. Results from a 2019 PMEL Saildrone mission that completed the first USV circumnavigation of Antarctica confirmed that under winter conditions, deep, CO2-enriched water churned to the surface could emit CO2 instead of absorbing it. That mission also demonstrated that a Saildrone could survive and collect high-quality scientific data in some of the harshest conditions on Earth.
The four Saildrones that will be used on the Southern Ocean mission are equipped with numerous hardy sensors (labeled above) that continuously collect data about the atmosphere and ocean, such as air temperature, sea temperature and salt concentration, and wind speed. (Image credit: Saildrone, Inc.)
The COCO2 team, joined by scientists from the University of Washington and South Africa’s Council for Scientific and Industrial Research and funded by Schmidt Sciences, is the first to deploy multiple USVs for an extended campaign in the Southern Ocean, said CSIRO scientist Elizabeth Shadwick.
“Saildrones will give us unprecedented coverage of regions that we can’t get to with research vessels or commercial ships in winter,” Shadwick said.
That’s when the Southern Ocean becomes a realm of monochrome isolation and staggering violence, as Earth’s rotation spawns hurricane-force winds that roar around the southern pole, driving a current so powerful it shapes the very climate of the planet.
“Getting the ocean’s carbon balance right is urgently important, but the Southern Ocean is one of Earth’s harshest environments and notoriously difficult to observe,” Sutton said. “This autonomous AI-directed ocean tech that takes on the risk of sailing in Southern Ocean storms is truly game-changing.”
Astrobiology, Oceanography, robotics,
