Arctic Ocean Currents Found to Speed Carbon-Rich Phytoplankton to the Seafloor

Scientists studying the Arctic's Chukchi Sea have found that ocean currents can transport carbon-rich phytoplankton to the seafloor much faster than previously observed. The research shows that certain current patterns can increase the sinking speed of these microscopic organisms to approximately four times their usual rate.

Phytoplankton are tiny organisms that use sunlight to absorb carbon dioxide through photosynthesis. They form the foundation of marine food webs and play an important role in the movement of carbon from the atmosphere and surface waters into deeper parts of the ocean.

Researchers from Stanford University's Doerr School of Sustainability studied phytoplankton growth and sinking behaviour during a research expedition in the Chukchi Sea in 2023. The team repeatedly sampled the region as it moved from open water into areas covered by sea ice.

The scientists discovered exceptionally dense phytoplankton populations beneath substantial sea ice. Some of these blooms were up to ten times more concentrated than those later observed in open water after seasonal ice retreat began.

As the blooms declined, much of the phytoplankton began sinking. In many parts of the sea, the material descended at approximately half a metre per day. However, where contrasting ocean currents met, the sinking process became considerably faster.

The researchers found that colder, saltier water moving from beneath the ice can encounter warmer and fresher water from the open sea. The interaction between these water masses creates a downward movement that carries phytoplankton towards the seabed.

The findings provide new information about the Arctic's carbon cycle. The researchers suggest that rapidly sinking phytoplankton could transfer carbon into seafloor sediments and influence marine ecosystems.

However, the researchers noted that continued Arctic warming could alter these processes. Changes in sea ice, freshwater input, ocean circulation and nutrient availability may affect both phytoplankton growth and the amount of carbon ultimately stored in the seafloor.

24-09-2026