As sunlight returns after the austral winter and sea ice begins to melt and shift, microscopic marine organisms start to grow rapidly in the Southern Ocean. These seasonal blooms support marine life across the region and play a role in drawing carbon from the atmosphere into the ocean. In one of the most remote parts of the planet, satellites offer a rare broad view of how these changes unfold.
The image, captured on 2 March 2026, shows part of the Cooperation Sea along the eastern coast of Antarctica. In the wider view, green-tinged waters spread through the ice pack, while a closer view reveals pale green streaks and filaments moving between sea-ice fragments. The colour points to high concentrations of phytoplankton near the ocean surface, shaped by currents and the changing ice cover.
Life beneath the ice edge
Phytoplankton are tiny organisms that live in the sunlit upper ocean and form the base of marine food webs. In Antarctic waters, their growth is strongly seasonal. During the dark winter months, production drops sharply. When light returns and the upper ocean becomes more stable, blooms can develop quickly.
Sea ice is central to that cycle. Its seasonal advance and retreat affect how much light reaches the water, how the ocean surface mixes, and how nutrients are distributed. Melting ice can help create a surface layer where phytoplankton remain in better-lit waters, allowing them to grow in large numbers. In some cases, the blooms become visible from space as green shades among the white and blue patterns of the sea ice.
These blooms matter far beyond their appearance. Phytoplankton feed krill and other small organisms that support fish, seabirds, seals and whales. They also absorb carbon dioxide through photosynthesis, making them part of the ocean system that helps regulate the climate. In Antarctica, where food webs are closely tied to the timing of ice and light, even small shifts in bloom patterns can have wider consequences.
A changing Antarctic ecosystem
Recent research suggests that changes in Antarctic sea-ice regimes are reshaping phytoplankton communities. A study published in Nature Climate Change examined observations from 1997 to 2023 and found evidence that the balance between major phytoplankton groups has been shifting as sea-ice conditions change.
The study reported a broad decline in diatoms in Antarctic shelf waters, alongside an increase in smaller groups such as haptophytes and cryptophytes. That matters because diatoms are especially important in the Southern Ocean. They are a major food source for Antarctic krill and are also linked to the transfer of carbon into deeper waters. A change in their abundance could therefore affect both marine ecosystems and the ocean’s role in storing carbon.
This makes satellite monitoring increasingly important. Observations from the Copernicus Sentinel missions help researchers detect blooms across remote polar seas and follow how they evolve over time. In Antarctica, where direct measurements remain limited by weather, ice and distance, satellite records provide a consistent way to monitor ocean colour, sea-ice conditions and seasonal change.
Seen from above, the green waters in this image are striking. But they also point to a larger story about the Antarctic marine environment. The patterns between the drifting ice fragments are not only a sign of life returning to the surface ocean at the end of summer. They are also part of a changing polar system in which sea ice, ocean conditions and microscopic plant life remain closely connected.
Featured image credit: European Union, Copernicus Sentinel-2 and Copernicus
