Robot Sailboats Will Spend Five Years Measuring Carbon in the Southern Ocean

The Southern Ocean covers almost a third of the world’s ocean surface and connects the basins of every other major ocean, with unforgiving conditions that make research difficult. Its extremely cold waters play a major role in the global carbon sink—the roughly 30% of anthropogenic carbon emissions absorbed each year—by the world’s oceans as a whole.

That combination of climate significance and physical inaccessibility makes monitoring and understanding how the Southern Ocean regulates the global atmosphere both critically important and exceedingly challenging. Closing that knowledge gap is a priority for researchers and governments around the world.

Led by researchers at the National Oceanic and Atmospheric Administration’s (NOAA) Pacific Marine Environmental Laboratory (PMEL) and Columbia University, the Constraining Ocean Carbon with Optimized Observing (COCO2) project is a five-year initiative that will deploy Saildrone uncrewed surface vehicles (USVs) to implement a novel and scalable approach to observing air-sea carbon exchange and reducing uncertainty in estimates of the global carbon sink. The USVs are small robotic sailing vessels equipped with onboard solar-powered sensors. They will spend many months at sea, sending real-time data to scientists from the remote and rough waters of the Southern Ocean that are often too difficult and expensive for research ships to reach.

At Columbia, the project will be led by Galen McKinley, a professor in the Department of Earth and Environmental Sciences within the Faculty of Arts and Sciences, and a researcher at the Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School.

COCO2 scientists launched the first USV from Hobart, Australia this week and will deploy an additional vehicle every three months until a total of four are successfully operating across the Southern Ocean.

“The Southern Ocean is one of Earth’s harshest environments and notoriously difficult to observe. With today’s launch, we bring together new tools to overcome this challenge and tackle long-standing questions about the ocean’s carbon sink,” said Adrienne Sutton of NOAA, who co-leads COCO2 with McKinley. “As a USV completes a circumnavigation of Antarctica, it will come back into Hobart, where sensors will be replaced, and the USV will be redeployed to start another circumnavigation. This pattern will continue for the duration of the five-year project.”

In addition to NOAA and Columbia, the other COCO2 collaborating institutions are the University of Washington, Australia’s national science agency, CSIRO, the Australian Antarctic Program Partnership, South Africa’s Council for Scientific and Industrial Research (CSIR) and its Southern Ocean Carbon-Climate Observatory (SOCCO), Schmidt Sciences and Saildrone.

“The Southern Ocean is central to the uptake and storage of CO2 from human emissions,” said CSIRO’s Elizabeth Shadwick. “The Saildrone USVs are expected to travel over 24,000 kilometers (13,000 nautical miles) for each deployment, giving us unprecedented coverage of regions that we can’t get to with research vessels or commercial ships. This will help fill critical gaps on how much carbon is being absorbed by the Southern Ocean, and what influences it.”

At Lamont, McKinley will lead the project’s data analytics and the USVs’ observing strategy, using machine learning tools to identify where additional measurements are needed.

“We will be able to make adjustments over the course of the five-year mission to target data collection in the regions that are most needed to better understand the ocean carbon sink,” said McKinley. “We will also apply advanced, model- and AI-observing tools to investigate carbon cycling in the Southern Ocean.”

CSIR provides critical observational capability and regional expertise. Schmidt Sciences, which supports targeted climate research to advance understanding of global carbon uptake, provides philanthropic funding through its Virtual Institute for the Carbon Cycle.

“The Southern Ocean plays an important role in the global climate system,” said CSIR’s Sandy Thomalla. “Understanding the processes controlling CO2 uptake is central to having accurate projections of the Southern Ocean carbon sink in the future.”

A treacherous ocean to sail

Compared to oceans in the Northern Hemisphere, the Southern Ocean is largely devoid of major landmasses, making it treacherous for crewed research vessels to transit safely. The region presents extreme operational hazards, including drifting icebergs, hurricane-force winds that generate massive waves, and vast distances from shore-based infrastructure.

Historically, safely observing the Southern Ocean has required chartering expensive research vessels, deploying large crews of mariners and scientists, and frequently losing valuable operational days to severe weather. Conditions become particularly difficult during austral winter, when ship-based research in parts of the Southern Ocean often stops altogether.

Uncrewed vehicles have already shown they can endure these conditions. In 2019, a Saildrone Explorer successfully circumnavigated Antarctica on a 196-day mission covering more than 11,000 nautical miles (20,000 km).

COCO2 will build on this success by deploying multiple Saildrone Explorer USVs year-round to monitor air-sea CO2 exchange in regions where critical data gaps remain. Because the vehicles operate without crews or chartered ships, the approach can be sustained through austral winter and scaled to cover far more of the ocean than vessel-based campaigns alone.

“The Southern Ocean is one of the most difficult places on Earth to operate, and that’s exactly the kind of challenge Saildrone was built for,” said Richard Jenkins, Saildrone founder and CEO. “COCO2 is an opportunity to put that capability to work on an ambitious international mission, providing sustained access to a region that has historically been extremely difficult to observe.”

Data collected through COCO2 will help improve estimates of how much carbon the Southern Ocean absorbs, and will feed directly into the Global Carbon Budget, an annual assessment of human CO2 emissions and how much of that total is taken up by land and oceans. The Global Carbon Budget is a critical mechanism by which the international community tracks progress toward the climate goals of the UNFCCC Paris Agreement.