Award: OPP-1941292

Overview: The Antarctic continent is fringed every summer by green waters indicating intense blooms of algae. These blooms are thought to play a key role in our climate by absorbing carbon dioxide from the atmosphere and mitigating greenhouse effects. However, this important contribution from blooms may or may not continue in the same way over the next century as this portion of the world is continuously exhibiting changes in water temperature, ice, and glaciers. The project focused on one of the most intense of these blooms (the Amundsen Sea bloom) and combined a research cruise and computer simulations to gain insight on how such blooms will evolve in the upcoming decades.

Intellectual merit: Numerical simulations representative of the middle of the 21st century provided a glimpse of what the Amundsen Sea bloom will look like in the future. Warmer temperatures cause larger openings in the ice cover, allowing in principle for additional sunlight for algal growth. However, we find that these gains are concentrated late in the summer season when the Sun is low over the horizon, which minimizes the benefits. In addition, the simulations reveal a weaker supply of an essential nutrient (iron). The overall outcome is that blooms such as the Amundsen's are likely to be larger in the future and to absorb more carbon dioxide, but not to the full extent suggested by the shrinking ice cover. Other lines of inquiries focused on where the iron necessary to the bloom is coming from, and in what ways. One study revealed that glaciers by themselves do not provide substantial amounts of iron. Instead, the presence of a "fluff layer" (representing remnants from the previous year's bloom) is thought to contribute to high iron concentrations observed near the sea floor. This deep iron is then mobilized toward the surface (where the algae reside) by the ocean circulation. A last study indicated that the ocean circulation in the vicinity of the glaciers is a robust feature of regions like the Amundsen Sea, and that future changes in the configuration of the glaciers are unlikely to slow it down.

Broader impacts: The simulations representative of the mid-21st century provide a key piece of information for future planning---although blooms like the Amundsen's are likely to absorb more carbon dioxide in the future, other aspects such as nutrient availability can ultimately limit this contribution. This result emphasizes the need for a diverse set of strategies and solutions. Additionally, information from the simulations conducted during the project helped to guide two research cruises in the Amundsen Sea (ARTEMIS and GP17-ANT) and interpret the measurements collected then. The project provided training with state-of-the-art technologies for five early-career participants who can leverage these skills in their next employment. Finally, the data generated by the project as well as the accompanying software are publicly archived and available to the private or public sectors.

Last Modified: 10/01/2026
Modified by: Pierre St-Laurent