Seasonal Response of River Plume to Freshwater Discharge in River-Dominated Ocean Margins: A Multi-Salinity Products Analysis and Inter-Regional Comparison
[14-Dec-2018] Feng, Y. and Menemenlis, D.
Presented at the 2018 AGU Fall Meeting
River plume dynamics generated considerable research interests for the past decade due to the important role in coastal ecology, biogeochemistry, shoreline morphology and climate. Previous investigators have utilized satellite ocean color or configured regional models in studying the dispersal of river plumes, with focusing on a certain continental shelf. In this study, we used high-resolution satellite sea surface salinity (SSS) observations and a globally configured 18-km resolution, eddy permitting model (ECCO2) with the river source improvement to investigate seasonal variability of river plumes at three continental shelves, namely the Northern Brazilian (NB) Shelf, the Northern Angola (NA) Basin, and the Texas-Louisiana (TL) Shelf. A comparison with World Ocean Database (WOD) showed that SMAP SSS Anomaly (SSSA) field had the smallest RMSE, followed by SMOS and ECCO2. Common river plume dispersal patterns were all well identified from the three products, including (1) the eastward transport of the Amazon River plume in July - November; (2) the southward dispersal of the Congo River plume in February-March; and (3) the July - September reversal of the Mississippi River plume. We also found that the plume area responded to freshwater discharge differently for these three regions. The response time is about 2 month for the NB shelf, 4 month for the NA Basin and 3 month for the TL shelf. About 50 -70% variability can be explained by freshwater discharge at the NB shelf and the NA Basin. In contrast, only about 20% can be explained at the TL shelf. The response time reflected the lag between the maximum river discharge and external forcing, primarily wind and ambient currents. The lower explained variance at the TL shelf is because the shelf located at higher latitude, resulting in the more bottom-advected river plume rather than the surface-advected. Our ensemble analysis provided strong support for river plume dynamic theories from idealized and realistic models.