Four uncrewed Saildrone Explorer vessels will take turns circling Antarctica over the next five years, each logging about 12,000 miles per lap while measuring how much carbon dioxide the Southern Ocean absorbs. The first drone left Hobart, Tasmania, on Sept. 19, 2026. Three more are planned for deployment at three-month intervals during 2027.
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NOAA announced the project on Oct. 13 alongside Columbia University, Australia’s national science agency CSIRO and other partners. Its goal is to collect measurements through the winter, the season when the region is hardest for crewed ships to reach and the one for which scientists have the thinnest records of how air and sea trade carbon dioxide.
COCO2 and its four sail-powered drones
The effort is called Constraining Ocean Carbon with Optimized Observing, or COCO2, and runs for five years. It is led by NOAA’s Pacific Marine Environmental Laboratory in partnership with Columbia University, CSIRO, the University of Washington and South Africa’s Council for Scientific and Industrial Research, with funding from Schmidt Sciences. The NOAA announcement says each vehicle completes the roughly 12,000-mile loop around the continent, then returns to port for repairs and refurbishment before heading out again. The project keeps its own public page, the COCO2 project site, and the vehicle maker has posted its own description of the expedition.
Routes are not fixed in advance. According to NOAA, AI-driven ocean-air models set the courses, steering the drones toward the high-value areas where measurements are likely to be most useful. That design lets a small fleet cover a very large and remote stretch of water, and it gives the scientists a way to adjust where each vehicle spends its time as conditions change across the five years of the mission.
The schedule staggers the launches rather than sending the whole fleet out at once. With the first vehicle already out of Hobart since Sept. 19, three more follow at roughly quarterly intervals through 2027, and each completes its roughly 12,000-mile lap before heading back to port for refurbishment and another deployment. Over five years that cycle of departures, laps and refits is meant to build a long, continuous record of air-sea carbon exchange in the part of the globe where such records are scarcest, instead of the single-season snapshots that a ship-based campaign typically yields.
The Southern Ocean carbon sink and the winter data gap
The ocean stores about a third of the carbon dioxide absorbed from the atmosphere each year, and scientists estimate the Southern Ocean accounts for 40% of that total, NOAA reports, citing 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. She added that adding winter observations fills a critical knowledge gap and does something traditional oceanographic tools have not managed.
The gap is a matter of access. Elizabeth Shadwick, a scientist at CSIRO, said the Saildrones will provide unprecedented coverage of regions that research vessels and commercial ships cannot reach in winter. NOAA frames the project as a response to that limitation: because traditional ships cannot easily gather winter observations, the agency says scientists are now turning to uncrewed systems that can stay at sea through the harshest part of the year in one of Earth’s most inhospitable environments.
A previous Saildrone trip showed why the season matters. In 2019 a NOAA-led mission became the first uncrewed surface vehicle to circumnavigate Antarctica, and it found that under winter conditions, carbon-rich deep water brought to the surface could release carbon dioxide rather than absorb it. That result is the reason the new mission is built around winter coverage, and it is why the partners want a continuous record rather than a handful of snapshots.
Instruments and where the data goes
Each drone carries sensors for direct, continuous measurement of the carbon dioxide exchanged between air and ocean. The same platforms record wind speed and direction, barometric pressure, solar radiation, relative humidity, air and sea surface temperature, salinity, chlorophyll and dissolved oxygen. Chlorophyll and oxygen readings speak to biological activity in the water, while the temperature and salinity measurements describe the physical conditions that influence how much gas the surface can take in.
The data will not stay inside the research community. NOAA’s Pacific Marine Environmental Laboratory will send observations to research users and to the World Meteorological Organization’s Global Telecommunication System, which carries data into weather models. Routing the readings into that system means the mission feeds weather prediction as well as climate research.
CSIRO, one of the partners, describes its mission on its own organization website. The project’s stated aim is more reliable estimates of how much carbon dioxide the Southern Ocean absorbs, and with the first vessel already underway from Tasmania, the first season of winter measurements is the next milestone to watch.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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