Princeton project expands to create a worldwide fleet of robotic floats to monitor ocean health

On October 29, the National Science Foundation (NSF) announced a $53 million grant — shared among a consortium of the country’s top ocean research institutions — to build a global network of chemical and biological sensors that will monitor ocean health.

Researchers lower a device into the water

The National Science Foundation is building out Princeton’s successful SOCCOM project, a fleet of ocean-monitoring robotic floats in the Southern Ocean, into a global network of floating ocean monitors. A single robotic float costs the same as two days at sea on a research ship, but floats can collect data autonomously for more than five years, in all seasons, including during winter storms when shipboard work is limited. Here, researchers deploy a SOCCOM biogeochemical float during a 2016/17 cruise of the R/V Palmer to the Southern Ocean.

Scientists at Princeton University, Monterey Bay Aquarium Research Institute (MBARI), University of Washington, Scripps Institution of Oceanography at UC San Diego and Woods Hole Oceanographic Institution will use this grant to build and deploy 500 robotic ocean monitoring floats around the globe. The new program builds on the successful Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project based at Princeton that has deployed similar floats in the ocean around Antarctica, proving their usefulness as year-round reporters of ocean chemistry and biological activity.

The new network of floats, called the Global Ocean Biogeochemistry Array (GO-BGC Array), will collect observations of ocean chemistry and biology between the surface and a depth of 2,000 meters.

“It’s exciting to see the transformative float technology proven in the SOCCOM project extended to all the world’s oceans,” said Jorge Sarmiento, Princeton’s George J. Magee Professor of Geoscience and Geological Engineering, Emeritus, and a co-principal investigator on the new project. “The GO-BGC array will give us an unprecedented 3-D view of global ocean biogeochemistry in real time and provide critical information we need to predict future changes in climate and ecosystems.”

Data streaming from the float array will be made freely available within a day of being collected, to be used by scores of researchers, educators and policy makers around the world.

These data will allow scientists to pursue fundamental questions about ocean ecosystems, observe ecosystem health and productivity, and monitor the elemental cycles of carbon, oxygen and nitrogen in the ocean through all seasons of the year. Such essential data are needed to improve computer models of ocean fisheries and climate, and to monitor and forecast the effects of ocean warming and ocean acidification on sea life, said the researchers.

Although scientists can use earth-orbiting platforms and research vessels to monitor the ocean, satellites can only monitor near-surface waters, and the small global fleet of open-ocean research ships can only remain at sea for relatively short periods of time. As a result, ocean health observations only cover a tiny fraction of the ocean at any given time, leaving huge regions unvisited for decades or longer.

A single robotic float costs the same as two days at sea on a research ship. But floats can collect data autonomously for more than five years, in all seasons, including during winter storms when shipboard work is limited.

Illustration of the devise gathering data

This illustration of the SOCCOM float observing system shows the deploying ship track (straight) along with the trajectories of three deployed floats, as well as communication of the float data back to land via satellites.

The GO-BGC Array is the National Science Foundation’s contribution to the Biogeochemical-Argo (BGC-Argo) project. It extends biological and chemical observing globally and builds on two ongoing efforts to monitor the ocean using robotic floats, both of which have been highly successful.

The first of these programs, the Argo array, consists of 3,900 robotic floats that drift through the deep ocean basins, providing information on temperature and salinity in the water column. Since its inception in 1999, Argo data have been used in 4,100 scientific papers. As the first global, subsurface ocean observing system, the Argo array has done an incredible job of measuring the physical properties of our ocean, but Argo floats do not provide information about the ocean’s vital chemical and biological activity.

Since 2014, NSF’s Princeton-based SOCCOM project has deployed almost 200 robotic “biogeochemical” floats, based on the Argo design but also carrying sensors to monitor the chemical and biological properties of the ocean. SOCCOM floats have operated for nearly six years in the remote, stormy and often ice-covered Southern Ocean — arguably one of the harshest marine environments on Earth. These floats have already provided critical new information about how the Southern Ocean interacts with the Earth’s atmosphere and winter sea ice.

Similar to the SOCCOM floats, the new GO-BGC floats will carry a number of sensors in addition to the core Argo sensors for temperature, depth and salinity. These include instruments to measure oxygen concentration, pH (ocean acidity), nitrate (an essential nutrient for microscopic algae), sunlight (required for algal growth), chlorophyll (an indicator of algal populations) and particles in the water (including microscopic algae). Over the last few years, researchers have been testing, refining and calibrating these sensitive instruments as part of the SOCCOM program and other international efforts.

A student next to the device

Then-graduate student Hannah Zanowski, who completed her Ph.D. from Princeton’s Atmospheric and Oceanic Sciences Program in 2017, went to sea in 2016 aboard the R/V Polarstern to help launch SOCCOM floats like this one.

The instruments on these floats will allow researchers to monitor the health of the ocean, including the growth and respiration of phytoplankton — drifting algae and microbes that use sunlight as a source of energy — and the nutrients and light that control these processes. In addition to supporting most of life in the ocean, including commercial fisheries, phytoplankton supply oxygen to and remove carbon dioxide from the ocean and the atmosphere. These microscopic plankton have huge impacts on our climate through their control on carbon dioxide. The new floats will also provide first-hand data on long-term changes in the ocean, including ocean acidification and the expansion of low-oxygen zones.

This five-year effort involves five research institutions. MBARI will coordinate the project, refine the sensors, take the lead in processing data from the floats and perform outreach for the program. The University of Washington, the Scripps Institution of Oceanography and the Woods Hole Oceanographic Institute will build and deploy floats in collaboration with commercial partners. Participants at Princeton will contribute to the array design and project management, and they will ensure that the data are linked to global computer models of the Earth’s ocean and climate. This program will also have a significant impact on the ocean technology industry, including a number of commercial suppliers of ocean sensors and profiling floats.

A broad public outreach program, including workshops, online curricula and hands-on activities, will help scientists, teachers, students and others use these data. In an expansion of the existing SOCCOM Adopt-A-Float program, the floats will be adopted by elementary- to college-level classes. Student activities will be developed through a partnership with the national Marine Advanced Technology Education program. In addition, courses based on GO-BGC technology will be offered through the The Sandbox, a makerspace at the Scripps Institution of Oceanography.

The researchers hope that GO-BGC will inspire other countries to contribute similarly instrumented floats, as part of the new global biogeochemical Argo effort. Ideally, this expanded network would double to a sustained array of 1,000 biogeochemical floats uniformly distributed around the world ocean, spaced about 1,000 kilometers (620 miles) apart.

Funding for the GO-BGC Array is provided through the NSF’s Mid-scale Research Infrastructure-2 Program (MSRI-2).