Quantifying freshwater fluxes from Major rivers and assessing their impact on the Atlantic Ocean
- 1Magellium (Ramonville-Saint-Agne, France)
Abstract
This study evaluates the impact of riverine freshwater fluxes on the Atlantic Ocean. The river discharge has been estimated at the outlet of 18 major rivers flowing into the Atlantic by solving the water mass balance equation at the river basin scale. In this approach, water storage changes are evaluated with satellite gravimetry measurements. In contrast, atmospheric fluxes (i.e., precipitation, evapotranspiration) are assessed with atmospheric reanalyses, in situ measurements from a global network of rain gauges, or a global hydrological model. The river discharge estimated with the water mass balance is consistent with independent river gauge measurements across all South American rivers, in particular the Amazon, where the annual and monthly climatology can be estimated with an error of less than 5 % when compared with in situ measurements. Larger discrepancies are observed for other basins, likely due to uncertainties in the precipitation and evapotranspiration fluxes. When climatological estimates of the river discharge are replaced by the water mass balance approach in ocean model simulations, a decrease in the sea surface salinity bias is observed at the outlet of the Amazon and across the whole Atlantic. The water mass balance approach can bring new observational constraints on freshwater fluxes flowing from the continent to the ocean, but is not universally reliable due to potential biases in atmospheric flux estimates. When combined with in situ measurements or hydrological model predictions, the water mass balance approach can enhance freshwater flux quantification, leading to improved ocean model simulations near major river outlets. In particular, the enhanced river runoff dataset significantly reduces salinity biases, with associated changes in vertical stratification, upper ocean circulation and basin scale meridional transports.
Versions
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BibTeX
@article{kern2026quantifying,
title = {{Quantifying freshwater fluxes from Major rivers and assessing their impact on the Atlantic Ocean}},
author = {Louis Kern and Thomas Vaujour and Julia Pfeffer and Andrea Storto and Camille Szczypta and Gilles Garric and Claire Sirere and Gilles Larnicol and Chunxue Yang and Romain Bourdalle-Badie and Stéphanie Guinehut},
journal = {Ocean Science},
year = {2026},
month = oct,
doi = {10.5194/os-22-3457-2026},
url = {https://os.copernicus.org/articles/22/3457/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Quantifying freshwater fluxes from Major rivers and assessing their impact on the Atlantic Ocean
AU - Louis Kern
AU - Thomas Vaujour
AU - Julia Pfeffer
AU - Andrea Storto
AU - Camille Szczypta
AU - Gilles Garric
AU - Claire Sirere
AU - Gilles Larnicol
AU - Chunxue Yang
AU - Romain Bourdalle-Badie
AU - Stéphanie Guinehut
PY - 2026
DA - 2026/10/28
JO - Ocean Science
DO - 10.5194/os-22-3457-2026
UR - https://os.copernicus.org/articles/22/3457/2026/
AB - This study evaluates the impact of riverine freshwater fluxes on the Atlantic Ocean. The river discharge has been estimated at the outlet of 18 major rivers flowing into the Atlantic by solving the water mass balance equation at the river basin scale. In this approach, water storage changes are evaluated with satellite gravimetry measurements. In contrast, atmospheric fluxes (i.e., precipitation, evapotranspiration) are assessed with atmospheric reanalyses, in situ measurements from a global network of rain gauges, or a global hydrological model. The river discharge estimated with the water mass balance is consistent with independent river gauge measurements across all South American rivers, in particular the Amazon, where the annual and monthly climatology can be estimated with an error of less than 5 % when compared with in situ measurements. Larger discrepancies are observed for other basins, likely due to uncertainties in the precipitation and evapotranspiration fluxes. When climatological estimates of the river discharge are replaced by the water mass balance approach in ocean model simulations, a decrease in the sea surface salinity bias is observed at the outlet of the Amazon and across the whole Atlantic. The water mass balance approach can bring new observational constraints on freshwater fluxes flowing from the continent to the ocean, but is not universally reliable due to potential biases in atmospheric flux estimates. When combined with in situ measurements or hydrological model predictions, the water mass balance approach can enhance freshwater flux quantification, leading to improved ocean model simulations near major river outlets. In particular, the enhanced river runoff dataset significantly reduces salinity biases, with associated changes in vertical stratification, upper ocean circulation and basin scale meridional transports.
SN - 1812-0792
ER -