In the spring of 2021, a multinational team of scientists embarked on a high-stakes expedition into the North Atlantic. Their mission was to solve a fundamental climate puzzle: how does organic carbon, created by life at the ocean’s surface, reach the deep sea for long-term storage? Battling both COVID-19 lockdowns and four massive storms with 50-knot winds, the NASA-led EXPORTS campaign has finally provided a definitive answer. The research reveals that violent storms act as a critical mechanical “reset” for the ocean’s biological carbon pump, shredding and then accelerating the sinking of “marine snow.”
The Ocean’s Biological Carbon Pump
The process begins with phytoplankton tiny photosynthetic organisms that fix roughly 55 to 60 billion metric tons of carbon annually. About 15% of this carbon eventually leaves the surface, hitching a ride on sinking particles. This movement of carbon from the atmosphere to the deep ocean is essential for moderating Earth’s climate, as sequestered carbon can remain out of the atmosphere for centuries or even millennia.
The most common vehicle for this journey is “marine snow”—fluffy, porous clumps of organic detritus. While individual phytoplankton cells sink at a rate of only one meter per day, these larger aggregates can plummet up to 100 meters daily. Understanding how these “dust bunnies of the ocean” behave in turbulent conditions has been a major challenge for oceanographers until now.
How Storms Trigger Carbon “Pulses”
The expedition discovered that storms affect carbon storage through a surprising two-step process. First, the violent turbulence of a storm shreds fragile marine snow into tiny fragments. Because smaller particles fall more slowly, this initially halts the downward flow of carbon. However, about two days after the storm passes, the team observed a massive “pulse” of sinking carbon.
This occurs because storms deepen the ocean’s mixed layer, stirring particles into deeper, calmer waters. When the winds die down and the surface layer stabilizes, the shredded particles no longer being tossed by waves begin to collide and reassemble into even larger, heavier aggregates. These newly formed clumps sink rapidly, effectively “flushing” the carbon into the deep sea.
The Role of Midwater Animals
The study also overturned long-held beliefs about what happens to carbon once it leaves the sunlit surface. By analyzing particles at depths of 200 to 500 meters, researchers found that large aggregates were being broken down at a rate of 12% per day. Contrary to existing models that credit microbes with this decay, the EXPORTS team found that zooplankton tiny midwater animals are the primary “editors” of sinking carbon.
These animals nibble, rasp, and repackage the falling marine snow, determining how much of it actually survives the trip to the seafloor. This biological activity, combined with the physical triggers of surface storms, creates a complex system that climate models have previously struggled to replicate.
Forecasting the Future
The insights gained from this storm-tossed expedition are now being woven into the next generation of Earth system models. By moving beyond simple descriptions to a predictive understanding of how turbulence and biology interact, scientists can better forecast how the ocean’s carbon valve will respond to a warming world. A global workshop scheduled for March 2026 in Glasgow will focus on embedding these “physics-plus-biology” findings into global carbon cycle simulations.
As UC Santa Barbara oceanographer David Siegel noted, the mission was a triumph of ingenuity over adversity, providing a clearer map of how our planet naturally tucks away excess carbon during the most violent of weather events.