Amazon River Plume Dynamics in the Tropical Atlantic Ocean

The Amazon River discharges an immense volume of freshwater into the western Tropical Atlantic, creating a buoyant plume that extends for thousands of kilometres. This plume strongly influences sea surface salinity, stratification and biogeochemical cycles. Seasonally, the plume is steered westward and northwestward by the North Brazil Current (NBC) and its retroflection, interacting with mesoscale rings that episodically detach from the NBC. These rings can advect low‐salinity water patches across the tropical gyre, modulating nutrient supply and creating barrier layers that inhibit vertical mixing. Wind‐driven Ekman currents and remote currents such as the North Equatorial Counter Current further shape plume pathways, while steric‐height anomalies mark freshwater‐induced sea‐surface undulations. The physical structure of the plume governs the distribution of nutrients, favouring blooms of diatom–diazotroph assemblages and other phytoplankton communities. Biogeochemical processing within the plume enhances carbon fixation, drives lateral CO₂ uptake, and influences air–sea gas exchange. Variability in river discharge and regional hydroclimate cycles amplifies plume extent and salinity contrasts, with implications for ocean circulation, tropical climate modulation and marine ecosystems.*

Research from Nature Portfolio

Recent studies have shown that intensification of the Amazon basin’s seasonal hydroclimate amplifies both river discharge and plume salinity cycles. Enhanced seasonal precipitation differences have been linked to stronger vertical and horizontal moisture advections, reinforcing the amplitude of plume‐induced salinity anomalies. Hierarchical climate model experiments demonstrate that these amplified seasonalities feed back on atmosphere–land–ocean coupling, potentially leading to more extreme marine and terrestrial conditions in the tropical Atlantic. Further global climate simulations indicate that sustained changes in Amazon runoff substantially alter sea surface temperature patterns and atmospheric circulation, with downstream impacts on the Atlantic Hadley cell and North Atlantic Oscillation–like anomalies. These findings underscore the sensitivity of tropical Atlantic dynamics to Amazon‐driven freshwater flux and its far‐field climatic consequences.*

Amazon River Plume Dynamics in the Tropical Atlantic Ocean publication trend

The graph below shows the total number of articles in amazon river plume dynamics in the tropical atlantic ocean across all publications each year (not limited to Nature Index journals).

Technical terms

Amazon River plume (ARP): Freshwater outflow from the Amazon River that spreads over the ocean surface, lowering salinity and affecting stratification.

North Brazil Current (NBC) rings: Anticyclonic eddies shed by the retroflection of the NBC, which can trap and transport plume water.

Mesoscale eddy: Ocean circulation feature 10–200 km in diameter that influences water parcel transport and mixing.

Barrier layer: A layer of relatively fresh, warm water above cooler, saltier water that suppresses vertical mixing.

Stratification: The layering of water masses of different density, often driven by salinity and temperature contrasts.

Diatom–diazotroph assemblage (DDA): Symbiotic partnership between diatoms and nitrogen‐fixing cyanobacteria that blooms in nutrient‐rich plume waters.

References

1. Late summer northwestward Amazon plume pathway under the action of the North Brazil Current rings. Remote Sensing of Environment (2024).
2. Combining an Eddy Detection Algorithm with In-Situ Measurements to Study North Brazil Current Rings. Remote Sensing (2023).
3. Amplified seasonal cycle in hydroclimate over the Amazon river basin and its plume region. Nature Communications (2020).
4. Long-term impact of Amazon river runoff on northern hemispheric climate. Scientific Reports (2017).
5. Top-down, bottom-up and physical controls on diatom-diazotroph assemblage growth in the Amazon River plume. Biogeosciences (2014).