An idealized study of near equatorial river plumes

ELBIO D. PALMA; RICARDO P. MATANO

JOURNAL OF GEOPHYSICAL RESEARCH

AMER GEOPHYSICAL UNION

Lugar: Washington; Año: 2017 p. 1 - 22

0148-0227

The dynamics of near-equatorial river plumes (NERPs) are investigated using a highlyidealized model. The spreading of a NERP from an eastern boundary is characterized by acontinuous shedding of westward propagating eddies. This process transfers the bulk of thefreshwater discharge to the deep ocean, thus distinguishing NERPs from their mid-latitudecounterparts. In the long-term limit a NERP can be rationalized as a B-plume emanatingfrom a coastal source. The evolution of NERPs in an unstratified basin is quite differentfrom that in a strafied one. The spin-up in an unstratified basin is characterized by theformation of an anticyclonic bulge, which spreads westward thus creating a densitystratification that favors the subsequent development of smaller and faster movingsecondary eddies. The collision of the secondary eddies with the leading bulge arrests theeffects of mixing thus allowing the further spreading of the buoyancy anomaly. In astratified basin the generation of anticyclonic eddies is accompanied by a concurrentgeneration of cyclones, which pump saltier waters to the surface hence leading to smallersea surface salinity (SSS) anomalies. NERPs are sensitive to variations of the freshwaterflux (Qfw) and the geomorphological setting. Larger Qfw generates bigger eddies, whichspread at a rate proportional to the square root of the normalized flux. Wide shelves allowthe interaction of the eddies with the bottom, thus promoting a cyclonic shift of the axis ofthe eddy train. The inclination of the coast affects the dynamical balance controlling thenear-field behaviour of NERPs.