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The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Numerical simulations.

Matano RP, Combes V, Piola AR, Guerrero R, Palma ED, Ted Strub P, James C, Fenco H, Chao Y, Saraceno M - J Geophys Res Oceans (2014)

Bottom Line: Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean.The net cross-shelf volume flux is 1.21 Sv.This outflow is largely compensated by an inflow from the Patagonian shelf.

View Article: PubMed Central - PubMed

Affiliation: College of Earth, Ocean and Atmospheric Sciences, Oregon State University Corvallis, Oregon, USA.

ABSTRACT

A high-resolution model is used to characterize the dominant patterns of sea surface salinity (SSS) variability generated by the freshwater discharges of the Rio de la Plata (RdlP) and the Patos/Mirim Lagoon in the southwestern Atlantic region. We identify three dominant modes of SSS variability. The first two, which have been discussed in previous studies, represent the seasonal and the interannual variations of the freshwater plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. A diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes. During the austral winter (JJA), the plumes leave the shelf region north of the BMC. During the austral summer (DJF), the plumes are entrained more directly into the BMC. A sensitivity study indicates that the high-frequency component of the wind stress forcing controls the vertical structure of the plumes while the low-frequency component of the wind stress forcing and the interannual variations of the RdlP discharge controls the horizontal structure of the plumes. Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean. The net cross-shelf volume flux is 1.21 Sv. This outflow is largely compensated by an inflow from the Patagonian shelf.

No MeSH data available.


Related in: MedlinePlus

Schematic of the SSS and circulation in the southwestern Atlantic region during summer and winter. The regions filled with light blue represent the spreading of the LPR and Patos/Mirim freshwater plumes. This schematic is based on the annual mean patterns from the child model and in situ observations.
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fig13: Schematic of the SSS and circulation in the southwestern Atlantic region during summer and winter. The regions filled with light blue represent the spreading of the LPR and Patos/Mirim freshwater plumes. This schematic is based on the annual mean patterns from the child model and in situ observations.

Mentions: We identify three dominant modes of SSS variability. The first two, which have been discussed in previous studies, represent the seasonal variations of the RdlP and the Patos/Mirim plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. The seasonal oscillations of this mode are partly driven by the dynamics of the western boundary currents and partly by the local wind stress forcing. A diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes. During the winter, northeasterly winds generate geostrophic currents that advect the plumes downstream leaving the shelf region north of the BMC (Figure 13). The low-salinity waters reaching the BMC during this season are drawn from the Patagonian shelf. During the summer, southwesterly winds generate currents that arrest the downstream spreading of the plumes funneling them into the BMC (Figure 13). Float trajectories suggest that the final destination of the shelf waters depends on their pathway over the shelf. The upstream pathway (summer) favors entrainment into the Southern Ocean. The downstream pathway (winter) favors entrainment into the Subtropical Gyre.


The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Numerical simulations.

Matano RP, Combes V, Piola AR, Guerrero R, Palma ED, Ted Strub P, James C, Fenco H, Chao Y, Saraceno M - J Geophys Res Oceans (2014)

Schematic of the SSS and circulation in the southwestern Atlantic region during summer and winter. The regions filled with light blue represent the spreading of the LPR and Patos/Mirim freshwater plumes. This schematic is based on the annual mean patterns from the child model and in situ observations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508930&req=5

fig13: Schematic of the SSS and circulation in the southwestern Atlantic region during summer and winter. The regions filled with light blue represent the spreading of the LPR and Patos/Mirim freshwater plumes. This schematic is based on the annual mean patterns from the child model and in situ observations.
Mentions: We identify three dominant modes of SSS variability. The first two, which have been discussed in previous studies, represent the seasonal variations of the RdlP and the Patos/Mirim plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. The seasonal oscillations of this mode are partly driven by the dynamics of the western boundary currents and partly by the local wind stress forcing. A diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes. During the winter, northeasterly winds generate geostrophic currents that advect the plumes downstream leaving the shelf region north of the BMC (Figure 13). The low-salinity waters reaching the BMC during this season are drawn from the Patagonian shelf. During the summer, southwesterly winds generate currents that arrest the downstream spreading of the plumes funneling them into the BMC (Figure 13). Float trajectories suggest that the final destination of the shelf waters depends on their pathway over the shelf. The upstream pathway (summer) favors entrainment into the Southern Ocean. The downstream pathway (winter) favors entrainment into the Subtropical Gyre.

Bottom Line: Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean.The net cross-shelf volume flux is 1.21 Sv.This outflow is largely compensated by an inflow from the Patagonian shelf.

View Article: PubMed Central - PubMed

Affiliation: College of Earth, Ocean and Atmospheric Sciences, Oregon State University Corvallis, Oregon, USA.

ABSTRACT

A high-resolution model is used to characterize the dominant patterns of sea surface salinity (SSS) variability generated by the freshwater discharges of the Rio de la Plata (RdlP) and the Patos/Mirim Lagoon in the southwestern Atlantic region. We identify three dominant modes of SSS variability. The first two, which have been discussed in previous studies, represent the seasonal and the interannual variations of the freshwater plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. A diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes. During the austral winter (JJA), the plumes leave the shelf region north of the BMC. During the austral summer (DJF), the plumes are entrained more directly into the BMC. A sensitivity study indicates that the high-frequency component of the wind stress forcing controls the vertical structure of the plumes while the low-frequency component of the wind stress forcing and the interannual variations of the RdlP discharge controls the horizontal structure of the plumes. Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean. The net cross-shelf volume flux is 1.21 Sv. This outflow is largely compensated by an inflow from the Patagonian shelf.

No MeSH data available.


Related in: MedlinePlus