Ocean robots explore ‘marine snow’ and carbon flow

A pioneering team of ocean robots and instruments is now at work in the icy depths of the Labrador Sea, part of a year-long scientific mission led by the UK’s National Oceanography Centre (NOC). The ReBELS project (Resolving Biological Carbon Export in the Labrador Sea) is delving into one of the ocean’s most vital climate functions: the biological carbon pump. This natural process plays a crucial role in drawing carbon dioxide from the atmosphere and storing it deep in the ocean. Without it, atmospheric CO₂ levels would be around 50% higher.

To better understand how carbon makes its way into the deep, the project is deploying a mix of advanced tools, including moored sensors, drifting floats and autonomous underwater vehicles. Together, they will track how carbon-rich particles, often referred to as ‘marine snow’, sink through the water column and how ocean dynamics such as deep convection may boost long-term carbon storage in this remote and little-studied region.

Tracking the speed of falling particles

At the heart of the effort is the FluxCAM, a new camera system built to measure the descent of marine snow particles of different sizes. By capturing how fast these particles fall, scientists hope to reduce key uncertainties in how much carbon the ocean actually removes from the atmosphere.

Two FluxCAMs were placed on a deep-sea mooring between Newfoundland and Greenland last year, alongside a specially calibrated profiling float. Now, autonomous underwater gliders have joined the mission, set to spend the next five to six months gathering data on ocean conditions and carbon flux throughout the water column.

“The biological carbon pump plays a crucial role in regulating Earth’s climate,” said project lead Dr Filipa Carvalho at NOC. “Microscopic marine plants, known as phytoplankton, absorb carbon dioxide from the atmosphere and convert it into organic material. This material is then consumed by marine organisms, with remnants eventually sinking as ‘marine snow’ – tiny carbon-rich particles that settle in the deep ocean, where the carbon can be stored for centuries.

“However, the rate at which these particles sink and how much carbon is ultimately locked away remain uncertain. The ReBELS project is using cutting-edge technology to answer these questions. This combination of fixed and mobile instruments will allow us to track how carbon is transported and transformed in the Labrador Sea over time,” Carvalho continued.

The cameras were installed at depths of 100 and 300 metres on a 3,300-metre-long mooring in the Labrador Sea, between Newfoundland and Greenland.

More frequent and varied depth profiles

The ReBELS profiling float has been programmed to perform more frequent and varied depth profiles than standard floats. It is also equipped with advanced sensors, including an optical sediment trap designed to measure the concentration of sinking particles while the float drifts at a fixed depth. One of the autonomous gliders will remain near the mooring site, while another will track the drifting float, collecting high-resolution data on particle dynamics, ocean circulation and biological activity.

“This combination of moored sensors, drifting instruments and mobile gliders is designed to overcome the challenges of studying carbon flux in the ocean,” said Dr Louis Clement, co-investigator and also at NOC. “While moored instruments provide long-term, fixed-location data, they do not capture the movement of water masses. The drifting float follows ocean currents, providing a dynamic perspective on sinking particles, while the gliders add another layer of insight, especially into small-scale turbulence effects on the biological carbon pump.

“By integrating data from these platforms, we hope to build the most accurate picture yet of carbon transport and storage in the Labrador Sea,” he added.

Funded by the Natural Environment Research Council (NERC), ReBELS is a four-year programme that builds on decades of scientific research into how the ocean stores carbon. Using advanced robotic technologies, the project aims to shed new light on the ocean’s role in regulating the climate, ultimately enhancing our ability to model and respond to global climate change.