New Study Reveals How Greenland’s Seaweed Stores Carbon in the Deep Ocean

An interdisciplinary study confirms, for the first time, the oceanographic pathways that transport floating macroalgae from the coastal waters of Southwest Greenland to deep-sea carbon reservoirs, potentially playing a previously underappreciated role in global carbon storage.

Macroalgae, or seaweeds (including kelp), are highly productive coastal habitats capable of absorbing significant quantities of atmospheric carbon (CO₂). Previous studies have estimated that globally, 4–44 teragrams (1Tg = one million metric tons) per year of macroalgal-derived carbon may reach depths of 200m, where it may be sequestered for at least 100 years.

However, macroalgae’s contribution to long-term carbon storage has been challenging to quantify with any certainty due to issues including: the wide range of macroalgae properties that need to be considered; the complexity of interactions with physical oceanographic transport processes, and a lack of scientific evidence about the travels and transformations of detached macroalgae after leaving coastal rocky shores.

To address this knowledge gap, the study team, co-led by the Leibniz Institute for Baltic Sea Research Warnemünde and Helmholtz-Zentrum Hereon in Germany and involving scientists from Plymouth Marine Laboratory, University of Exeter, Portugal, Saudi Arabia and Denmark, used a combination of satellite imagery, ocean drifter tracking, numerical modelling and advanced turbulence