Australian research reveals key role of windblown dust in Southern Ocean's carbon storage

Windblown dust from the continents fuels one-third of the phytoplankton growth in the Southern Ocean, Australian research has found.

In a study published on Thursday, a team from the Australian Research Council, the Centre of Excellence for Climate Extremes, the Commonwealth Scientific and Industrial Research Organisation, and the University of Tasmania revealed the role of dust in the ocean's capacity to store carbon dioxide (CO2).

Phytoplankton are microscopic algae that form the base of marine food webs and use CO2 to convert sunlight into food.

When plant-like organisms die and sink to the bottom of the ocean, the CO2 absorbed into their biomass is stored for long periods of time, effectively removing the greenhouse gas from the Earth's atmosphere. Separate research published by NASA in 2021 found that the Southern Ocean absorbs more carbon from the atmosphere than it releases.

In the study published on Thursday, researchers estimated that windblown dust from the continents fertilizes one-third of phytoplankton growth in the Southern Ocean.

"Dust carried from the continents by winds provides phytoplankton with iron, an essential micronutrient in short supply in the Southern Ocean," Jakob Weis, lead author of the study, said in a media release.

"For the first time, our study shows that windblown iron-rich dust from land 'fertilizes' around a third of phytoplankton growth in the Southern Ocean, making dust-fueled productivity a significant contributor to the ocean's capacity to store carbon."

The team made the discovery by measuring concentrations of nitrate – another essential nutrient for phytoplankton growth – at over 13,000 locations in the Southern Ocean using a fleet of ocean robots.

By measuring how much nitrate was disappearing, they calculated phytoplankton growth and compared the estimates with simulated dust depositions.

Weis said the findings would help forecast phytoplankton growth in the future as drier or windier conditions cause rapid changes in dust depositions in the ocean.