The Congo River discharges an average of 40,000 cubic meters of fresh water per second into the Atlantic Ocean, creating a large plume that extends 800 kilometers offshore. According to research published in the Journal of Geophysical Research: Oceans, this freshwater transport is influenced by large, rotating ocean currents known as mesoscale eddies, which can carry low-salinity water hundreds of kilometers from the coast.
How do mesoscale eddies move river water?
Mesoscale eddies act as transport vessels for the Congo’s freshwater discharge. These rotating currents, which have sizes on the order of 100 kilometers, often trap low-salinity water from the river plume during the wet season. Research conducted by Cardot et al. at the Laboratory of Space Geophysical and Oceanographic Studies (LEGOS) found that these eddies shift the plume’s trajectory toward the southwest. Once the fresh water is caught in the core of an eddy, it is transported significant distances before the eddy dissipates.
One anticyclonic eddy observed in 2016 lasted for 49 days, growing to a radius of 150 kilometers. It successfully transported fresh water roughly 200 kilometers offshore before dissipating.
How did researchers track the Congo River plume?
To map the movement of the Congo River discharge, scientists utilized the Nucleus for European Modelling of the Ocean (NEMO) circulation model. According to the study, the team employed a 3-kilometer ocean circulation model to simulate 2016 conditions. This specific year was chosen due to the availability of observational records from the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA) and satellite records of salinity and currents in the region.
The research team validated their model by comparing simulated results against measurements. This included data on sea surface salinity, sea surface height, and surface current data. The validation process also incorporated ship-tracking data processed by eOdyn through the Automatic Identification System (AIS), which confirmed that the model accurately reflected the size, position, and seasonal changes of the plume.
Why is tracking freshwater discharge important?
Understanding the path of the Congo River’s discharge is a focus of study. Because the river is the second largest river in the world, its freshwater input alters the local salinity and density of the ocean. By identifying how mesoscale eddies redistribute this fresh water, scientists can better understand how fresh water moves from the Congo River into the Atlantic Ocean. This work provides a picture of the interaction between major river systems and ocean circulation patterns.
Frequently Asked Questions
What is a mesoscale eddy?
A mesoscale eddy is a large, rotating current in the ocean, with sizes on the order of 100 kilometers. These features are known for trapping and transporting water masses across long distances.
How much water does the Congo River release?
The Congo River releases an average of 40,000 cubic meters of water per second into the Atlantic Ocean, making it the second largest river in the world.
Why does the Congo River plume shift?
The plume shifts seasonally, particularly during the wet season. During these periods, the fresh water can be trapped by mesoscale eddies, which redirect the flow toward the southwest.
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