Free-Floating Robots Find Ocean’s Carbon Storage Is Struggling

Free-Floating Robots Reveal Ocean's Struggling Carbon Storage

In the depths of the ocean, a hidden fleet of robotic devices is listening for signs of stress inside the planet's largest life-support system. These autonomous "biogeochemical" profiling floats, part of the U.S.-led Global Ocean Biogeochemical (GO-BGC) Array, are collecting data in near-real time to understand how the ocean's carbon cycle is responding to climate change.

Understanding the Ocean's Carbon Cycle

The ocean's carbon cycle is a complex process that involves the exchange of carbon dioxide (CO2) between the atmosphere and the ocean. When plankton grow at the surface and die, or are eaten by other plankton or fish, the resulting organic material falls through the water column as tiny particles or fecal pellets. This process is critical to how Earth stores CO2, and it's a key area of research for scientists like Ken Johnson, a senior scientist at the Monterey Bay Aquarium Research Institute (MBARI) and lead principal investigator for the GO-BGC program.

How Biogeochemical Robots Work

In a typical cycle, BGC-Argo floats drop to roughly 1,000 meters and drift for 10 days, following a specific water mass. Each float has a central processor that synchronizes readings from the onboard sensors, including oxygen, pH, nitrate, suspended particles, chlorophyll, and temperature, conductivity, and depth. A buoyancy pump expands and contracts an external oil bladder, letting it dive to 2,000 meters before rising again and collecting continuous measurements on the way up. When its antenna reaches the surface, the float transmits its data through the Iridium satellite network, and immediately sinks again.

The Importance of Continuous Monitoring

High-precision ship-based surveys provide detailed data but are restricted by schedules, weather, and cost. Satellites are largely limited to the surface and upper sunlit layer of the ocean, and cannot directly observe deeper water columns. But the floats will do it all year round, even on Christmas and Thanksgiving, and in the winter when the weather is terrible and no one wants to be out there.

What the Robots Reveal

MBARI's new study in Nature Communications used the floats to observe the aftermath of a massive North Pacific marine heatwave in the Gulf of Alaska from 2013 to 2015 (called "The Blob") and its 2019 to 2020 successor. The researchers paired float readings with seasonal data from ship-based surveys tracking plankton pigments and environmental DNA from seawater samples collected by Fisheries and Oceans Canada's Line P program. The study found that the heatwaves caused changes in ecosystem structure—in the plankton and how they operate—and these shifts in carbon export and how the ocean sequesters carbon are changing the services the ocean provides to us in ways we hadn't really appreciated.

Implications for Climate Change

The ocean gives us seafood, it absorbs about 95 percent of the anthropogenic heat in the atmosphere, it stores a bunch of CO2. We can now see that its ability to continue providing those services isn't a given. It can be altered by a heatwave. The study's findings have significant implications for our understanding of the ocean's role in the global carbon cycle and its response to climate change.

Future Directions

The program's future isn't guaranteed without additional support. The $53 million NSF grant that built the U.S. BGC-Argo fleet expires this year, and Johnson says no continuation funding has been secured yet. However, the research has already led to the development of new biogeochemical insights, including the use of machine learning techniques to extract new insights from the float data. The study's findings highlight the importance of continued investment in oceanographic research and the need for a sustained commitment to understanding the ocean's role in the global carbon cycle.

Conclusion

The free-floating robots are revealing the ocean's struggling carbon storage, and the implications are significant. The ocean's ability to sequester carbon is changing, and this has major implications for our understanding of the global carbon cycle and its response to climate change. The research has already led to new insights and understanding of the ocean's role in the global carbon cycle, and it highlights the importance of continued investment in oceanographic research.

Source: https://spectrum.ieee.org/ocean-robots-mbari-bgc-argo