Mesoscale ocean eddies regulate pathways that move carbon from the surface ocean into the deep sea by coupling physical circulation with biological processes. Mesoscale eddies are rotating water masses roughly 10 to 200 kilometers across that generate vertical motions and lateral transport; these motions modulate nutrient availability, plankton community structure, and the fate of organic particles.
Physical mechanisms driving export
Cyclonic eddies induce upward motion that can inject nutrients into the sunlit layer, fueling phytoplankton growth and enhancing the biological pump. Dennis McGillicuddy at Woods Hole Oceanographic Institution has demonstrated through observations and modeling that such eddy-driven nutrient injections can create localized blooms and elevated particle production. Conversely, anticyclonic eddies often cause downwelling and can trap organic matter, promoting subduction of surface-produced organic carbon into interior waters. Observations from ship surveys, floats, and satellites show that both upward and downward eddy dynamics alter vertical fluxes of particulate organic carbon.
Biological and ecological consequences
Enhanced primary production inside productive eddies increases the formation of sinking particles through aggregation and zooplankton feeding, and David M. Karl at University of Hawai‘i has documented episodes where eddy-associated processes coincide with elevated particulate export measured beneath the euphotic zone. This enhancement is not uniform; export efficiency depends on plankton community composition, grazing pressure, and particle remineralization rates. In oligotrophic gyres, a nutrient pulse can temporarily shift microbial food webs toward larger phytoplankton that sink more readily, while in productive boundary regions eddy stirring may export already abundant biomass laterally.
Human and environmental implications extend beyond carbon budgets. Eddy-modulated productivity affects fisheries around island and coastal communities, altering local food security and economic livelihoods. Eddies also influence oxygen and nutrient distributions in subsurface waters, with consequences for habitat quality and biogeochemical cycling at regional scales.
Collectively, observations and models indicate mesoscale eddies are essential regulators of carbon export pathways. Continued coupling of remote sensing, targeted ship campaigns, and autonomous platforms is required to quantify their net contribution across different ocean provinces and in a changing climate where eddy characteristics may shift, altering both carbon sequestration and regional ecosystem services.